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150+ Marks Guaranteed: RAY OPTICS AND OPTICAL INSTUMENTS | Quick Revision 1 Shot | Physics for NEET

YAKEEN・188 minutes read

Ray optics in the 12th-grade syllabus focuses on curved mirrors, lenses, and optical instruments, requiring a strong grasp of formulas and laws of reflection. Understanding refractive index, angles, and image formation is crucial for solving problems effectively and determining image characteristics in mirrors and lenses.

Insights

  • Ray optics is a significant chapter in the 12th class syllabus, often considered challenging but not as tough as rotation.
  • Understanding the formulas in ray optics is crucial for solving numerical problems effectively, with NEET previous year questions being a helpful resource.
  • The speed of light in different mediums is determined by the permeability of the medium and the speed of light in a vacuum, with refractive index being a key concept.
  • The laws of reflection dictate that incident rays, normals, and reflected rays lie in the same plane, with angles of incidence and reflection being equal.
  • The angle between incident and reflected rays is always twice the angle of incidence, with practical applications in determining angles of reflection in various scenarios.
  • The process of creating images through reflection and refraction in lenses and mirrors is explained, emphasizing the importance of understanding the path of light rays.

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Recent questions

  • What is the significance of ray optics?

    Ray optics is a crucial chapter in the 12th class syllabus, considered challenging but not as tough as rotation. It involves conventions and various topics, with four questions consistently asked every year focusing on curved mirrors, plane mirrors, refraction, lenses, and optical instruments. Understanding the formulas in ray optics is essential for solving numerical problems effectively, with NEET previous year questions being a helpful resource.

  • How is the speed of light in different mediums determined?

    The speed of light in different mediums is determined by the permeability of the medium and the speed of light in a vacuum, with refractive index being a key concept. The refractive index is inversely proportional to the wavelength of light, with shorter wavelengths having higher refractive indices. The laws of reflection dictate that incident rays, normals, and reflected rays lie in the same plane, with angles of incidence and reflection being equal.

  • What is the formula for calculating the number of images formed by two parallel mirrors?

    The number of images formed by two parallel mirrors is calculated by dividing 360 by the angle between the mirrors. If the number of images is odd, it indicates symmetry in the object's placement; if even, it suggests asymmetry. The angle at which an object is placed between two mirrors determines the angles at which the images will be formed.

  • How is the focal length of a convex lens determined?

    The focal length of a convex lens is determined by the formula f = -r * (1/n - 1), where n is the refractive index. For a biconvex lens, the focal length is equal to r divided by 2. Placing a glass lens in water alters the focal length, with the focal length in water being four times that in air. The nature of a lens, whether converging or diverging, is determined by the refractive index compared to the medium.

  • What is the process of image formation in a compound microscope?

    A compound microscope combines an objective lens and an eyepiece to enhance clarity, with magnification being the product of both lenses. The magnification of a compound microscope is determined by the focal lengths of the lenses, with a higher magnification achieved by reducing the focal length. The length of a compound microscope is the sum of the focal lengths of the objective and eyepiece lenses. The magnification at the near point is maximum, while at the far point, the image becomes infinity.

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Summary

00:00

Ray Optics: Essential Principles and Formulas

  • Ray optics is a significant chapter in the 12th class syllabus, often considered challenging but not as tough as rotation.
  • Ray optics involves conventions and various topics, with four questions consistently asked every year, focusing on curved mirrors, plane mirrors, refraction, lenses, and optical instruments.
  • Understanding the formulas in ray optics is crucial for solving numerical problems effectively, with NEET previous year questions being a helpful resource.
  • The speed of light in different mediums is determined by the permeability of the medium and the speed of light in a vacuum, with refractive index being a key concept.
  • The refractive index is inversely proportional to the wavelength of light, with shorter wavelengths having higher refractive indices.
  • The laws of reflection dictate that incident rays, normals, and reflected rays lie in the same plane, with angles of incidence and reflection being equal.
  • Deviation in light rays occurs when they reflect off plane mirrors, with the angle of deviation being calculated based on the total angle of incidence and reflection.
  • Inclined mirrors can lead to complex angles of reflection, requiring an understanding of the laws of reflection to calculate accurately.
  • The angle between incident and reflected rays is always twice the angle of incidence, with practical applications in determining angles of reflection in various scenarios.
  • Understanding the principles of reflection and refraction in ray optics is essential for solving problems and answering questions effectively.

15:03

Mirror Reflection and Image Formation Principles

  • The angle between the incident ray and the plane mirror is referred to as alpha.
  • The angle between the incident rays is denoted as theta.
  • The total angle formed by a straight line is 180 degrees.
  • Deviation from normal incident is equal to 180 - 2 times the incident angle.
  • Two plane mirrors interacting can result in a total deviation of 360 degrees.
  • The deviation between two plane mirrors can be calculated as 360 - 2 times the angle between the mirrors.
  • Rotating a plane mirror by theta while keeping the incident ray fixed results in the reflected ray turning by 2 times theta in the same sense.
  • If a mirror rotates by theta, the reflected ray turns by 2 times theta in the same sense.
  • Image formation by a plane mirror does not depend on the mirror's size.
  • The visibility of the image depends on the size of the mirror, and covering part of the mirror does not change the image size but affects brightness.

30:31

Mirror Height, Image Number, and Angles

  • The height of a mirror is determined by the distance between the object and the mirror, as well as the angle of incidence and reflection.
  • The number of images formed by two parallel mirrors is calculated by dividing 360 by the angle between the mirrors.
  • The number of images formed by two plane mirrors can be determined by subtracting 1 from the result of 360 divided by the angle between the mirrors.
  • If the number of images is odd, it indicates symmetry in the object's placement; if even, it suggests asymmetry.
  • The angle at which an object is placed between two mirrors determines the angles at which the images will be formed.
  • The total angle between the two mirrors and the angle of the object's placement dictate the angles at which the images will be formed.
  • The number of images formed by a mirror at a specific angle is calculated by dividing 360 by the angle.
  • The number of images formed by a mirror at a 10-degree angle is determined by subtracting 6 from the result of 360 divided by the angle.
  • The angles at which images are formed by two mirrors are calculated by adding the angles of the mirrors and the object's placement.
  • Images formed by mirrors will always be located behind the object, at an angle of at least 180 degrees from the original position.

44:50

"Mirror angles impact image creation formula"

  • The plane mirror should not exceed 180 degrees in angle.
  • Increasing the angle between plane mirrors results in fewer images being produced.
  • The number of images created is affected by the angle between the mirrors.
  • Objects placed at different angles from the mirrors result in varying numbers of images.
  • The total number of images created is determined by the angle between the mirrors.
  • The angle between the mirrors should not exceed 180 degrees to ensure valid image creation.
  • The distance between two parallel plane mirrors impacts the number of images produced.
  • The distance between the object and the mirrors influences the location of the images.
  • The formula for calculating the number of images involves the object distance and the distance between the mirrors.
  • Understanding the sign conventions and proper use of formulas is crucial in determining image characteristics in spherical mirrors.

58:26

"Mirror Image: Focus, Size, and Magnification"

  • The image is created based on the object's position, with a table used to illustrate the concept.
  • Moving the object from infinity towards the focus results in the image coming into focus and becoming larger.
  • The size and distance of the image depend on the focus, with objects out of focus appearing smaller and farther away.
  • P images are created when the object is near infinity and in focus, with the image becoming virtual as the object moves.
  • The focal length of a concave mirror is negative, leading to real or virtual images based on the image distance.
  • Convex mirrors have the highest field of view, making them ideal for use in cars' side mirrors.
  • Velocity of image equals the velocity of the object multiplied by the transverse magnification.
  • The speed of the object determines the position of the image after a certain time, with different scenarios for plane and concave mirrors.
  • Magnification determines the nature of the image, with negative magnification indicating an inverted image.
  • The distance between an object and its two times magnified virtual image produced by a curved mirror can help determine the mirror's focal length.

01:13:45

Mirror and Lens Magnification and Focal Length

  • Magnification is always less than one in a convex mirror.
  • Convex mirrors create virtual and smaller images between the focus.
  • Concave mirrors can be made smaller or larger.
  • Magnification of a concave mirror is less than one.
  • Magnification of a convex mirror is always less than one.
  • Focal length of a concave mirror is negative.
  • Focal length of a concave lens is negative.
  • Transverse magnification is minus v divided by u.
  • Newton's formula is f = √(x * y) where x is the object distance and y is the image distance from the focus.
  • Velocity of image equals MT when the object moves perpendicular to the principal axis.

01:28:30

Optical Physics Formulas and Concepts

  • Formula A: Refracted ray equals real depth divided by refractive index
  • Virtual Depth: Virtual depth divided by refractive index of the medium
  • Relative Refractive Index: Object's medium relative to observer's medium
  • Ice Cube Bubble: Apparent distance of bubble is 12 cm
  • Refractive Index Calculation: Refractive index equals h1 divided by h2
  • Plane Mirror: Image distance from bottom of tank is 42 cm
  • Critical Angle: Angle of refraction equals 90 degrees at critical angle
  • Total Internal Reflection: Incident angle less than critical angle leads to total internal reflection
  • Critical Angle Values: Critical angle for glass is 49 degrees, for air is 42 degrees
  • Radius of Visibility: Radius equals h divided by square root of refractive index difference

01:43:29

Calculating Areas, Angles, and Refractive Indices

  • The area of three circular wicks with a radius of 3 meters is calculated using the formula pi R squared.
  • The value of x is determined by the equation given in the text.
  • The concept of critical angle and image formation is explained.
  • The formula for critical angle in terms of angular velocity is discussed.
  • The speed of light in different mediums and the concept of refractive index are elaborated upon.
  • The relationship between velocity, wavelength, and refractive index is explained.
  • The process of image formation in refracting surfaces is detailed.
  • The formula for calculating object and image distances in different mediums is provided.
  • A question involving transparent media with different refractive indices is presented.
  • The lens maker formula for determining focal length in lenses is discussed.

01:58:58

Lens Curvature and Focal Length Determination

  • The formula or requirement for the first surface of a lens involves measuring the radius of curvature of the other surface.
  • The convex lens is referred to as a Bi-convex lens.
  • The radius of curvature of the first surface is denoted as r1, while the second surface's curvature is r2.
  • When measuring the radius, r1 is positive, and r2 is measured from the center of the surface.
  • The focal length of a convex lens is determined by the formula f = -r * (1/n - 1), where n is the refractive index.
  • For a biconvex lens, the focal length is equal to r divided by 2.
  • Placing a glass lens in water alters the focal length, with the focal length in water being four times that in air.
  • The nature of a lens, whether converging or diverging, is determined by the refractive index compared to the medium.
  • A convex lens converges light rays, while a concave lens diverges them.
  • Image formation in a convex lens differs from that in a concave mirror, with real images formed on the opposite side in lenses.

02:13:39

Lens Cutting and Power Calculation Formulas

  • Axis of a lens is cut into two halves perpendicular to the principal axis
  • The lens is separated into three lenses
  • The power of lens one remains the same after being cut
  • The power of lens is calculated using the formula P = 1/f
  • The number of images formed by dividing a lens into parts in different mediums is discussed
  • The formula for power of multiple lenses in contact is explained
  • The distance between an object and its three times magnified virtual image produced by a convex lens is given as 20 cm
  • The lens formula 1/v - 1/u = 1/f is used to calculate the focal length
  • The displacement method for determining the focal length of a lens is described
  • The importance of magnification and the product of magnifications in different lens positions is emphasized

02:28:09

Lens magnification formulas and practical applications

  • The formula for magnification in different cases is discussed, with m1 and m2 representing magnifications in the first and second cases respectively.
  • The magnification formula is f = m1 * m2 * b, where f is the focal length and b is the distance between the lenses.
  • The position of the lens in both cases is determined by x divided by the distance between them.
  • The product of magnification in the first case is calculated by multiplying the magnifications in both cases.
  • The height of the object and image in both cases is determined by a formula involving the square root.
  • The distance between positions divided by 1 - the direct sum in the displacement method is used to calculate the length of both lenses.
  • Questions related to lens and mirror combinations are discussed, including scenarios where lenses are cut in half and the focal length of the half part is determined.
  • Practical questions involving glass with water, object height, and distance between lenses are addressed using formulas.
  • The process of creating images through reflection and refraction in lenses and mirrors is explained, emphasizing the importance of understanding the path of light rays.
  • The concept of silvering off lenses is introduced, where lenses behave like mirrors after being coated with a reflective material.

02:43:35

Lens and Mirror Focal Length Formulas

  • Silvering the convex lens changes its focal length
  • Concave mirror's focal length is derived without the lens formula
  • Concave lens is explained and its focal length discussed
  • Differences between concave and convex mirrors are highlighted
  • Focal length of concave mirror is negative
  • Formula for deriving focal length is detailed
  • Plano-convex lens characteristics and focal length are explained
  • Calculation of net focal length for plano lens is outlined
  • Prism's definition, refracting angles, and deviation are discussed
  • Minimum deviation concept and its formula are elucidated

02:58:42

Prism Deviation and Dispersion in Optics

  • Deviation occurs if the angle of incidence is very low, leading to a small angle of prime.
  • Deviation is defined as the angle off prime.
  • 90 questions will be of prime, with five questions solved on one page.
  • The formula for minimum deviation is solved using Snell's law.
  • The formula for delta minimum is 2 times the angle of incidence minus the angle of emergence.
  • The dispersion of light through a prism results in different colors spreading based on their wavelengths.
  • The mean deviation is calculated by dividing the sum of the refractive indices of violet and red by 2.
  • Dispersive power is the ability to spread light, with a higher power indicating more dispersion.
  • The condition for no deviation in two prisms involves making the dispersive angles of both prisms equal.
  • Optical instruments are used for angular magnification to view objects with a specific height.

03:14:27

"Enhancing Vision: Microscope Magnification Explained"

  • The maximum capability of eyes is the ability to see clearly, with a viewing capacity of 25 cm.
  • The visual angle of an object is determined by the naked eye, without the use of lenses or mirrors.
  • A simple microscope utilizes a convex lens to magnify objects, with a maximum magnification of nine times.
  • Magnification in a simple microscope is calculated using the formula d/f or 1/p*d.
  • A compound microscope combines an objective lens and an eyepiece to enhance clarity, with magnification being the product of both lenses.
  • The magnification of a compound microscope is determined by the focal lengths of the lenses, with a higher magnification achieved by reducing the focal length.
  • The length of a compound microscope is the sum of the focal lengths of the objective and eyepiece lenses.
  • The magnification at the near point is maximum, while at the far point, the image becomes infinity.
  • The magnification of a compound microscope is higher when the object distance is equal to the focal length of the eyepiece.
  • To achieve maximum magnification in a compound microscope, the object distance should be set equal to the focal length of the eyepiece, resulting in a significantly enlarged image.

03:31:20

Microscope and Telescope: Length and Magnification

  • The length of a compound microscope is crucial for creating an image, with the image being approximately equal to the length of the compound.
  • Telescopes utilize lenses to see distant objects by focusing parallel rays, creating images at the focal length of the objective.
  • Magnification in telescopes is determined by the ratio of the height of the image to the height of the object, with a simple formula to calculate it.
  • The length of a telescope is determined by the focal length of the objective lens, with magnification being affected by the distance between the lens and the eye.
  • Scattering of light in the atmosphere is inversely proportional to the wavelength, with the refractive index of the medium affecting the scattering process.
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