CUET  >  Reflection - Physics

# Reflection - Physics - General Test Preparation for CUET

 Table of contents Reflection Laws of reflection: Reflection in a concave & convex mirror Refraction at a Plane Surface Refraction by Spherical Lenses Optical Instruments Physics

## Reflection

• The phenomenon due to which a beam of light, travelling through a certain medium, on striking some surface, bounce off from it in some other direction is called reflection of light.

## Laws of reflection:

1. The incident ray, the reflection ray and the normal at the point of incident lie in the same plane.
2. Angle of incidence is always equal to angle of reflection.
3. When the two mirrors are placed at certain angle to each other then number of images formed will be,
n = (360 / Ø)-1
4. The least size of the mirror required is half the height of the observer

### Characteristics of image

• If the image is erect and of the same size as the object and it appears to be formed behind the mirror, the reflecting surface is plane.
• If the image is erect and formed behind the mirror but diminished in size for all positions of the mirror, the mirror must be convex.
• If the image is erect, formed behind the mirror and enlarged, then the mirror is concave.

## Reflection in a concave & convex mirror

Reflection

Reflection of light on a concave mirror
Reflection of light on a convex mirror

 Position of the object Position of the image Size of the image Nature of the image At infinity At the focus F Highly diminished, point-sized Real and inverted Beyond C Between F and C Diminished Real and inverted At C At C Same size Real and inverted Between C and F Beyond C Enlarged Real and inverted At F At infinity Highly enlarged Real and inverted Between P and F Behind the mirror Enlarged Virtual and erect

### Uses of concave mirrors

• Concave mirrors are commonly used in torches, search-lights and vehicles headlights to get powerful parallel beams of light.
• They are often used as shaving mirrors to see a larger image of the face.
• The dentists use concave mirrors to see large images of the teeth of patients.
• Large concave mirrors are used to concentrate sunlight to produce heat in solar furnaces.

### Images by convex mirrors

 Position of the object Position of the image Size of the image Nature of the image At infinity At the focus F, behind the mirror Highly diminished, point-sized Virtual and erect Between infinity and the pole P of the mirror Between P and F, behind the mirror Diminished Virtual and erect

## Refraction at a Plane Surface

• When a ray of light passes from one medium to other it suffers a change in direction at the boundary of separation of two media.
• This phenomenon is called refraction.
• When a ray of light travels from one medium to another the wavelength and velocity of light change but the frequency does not change.

Refraction

## Refraction by Spherical Lenses

Refraction by Converging LensRefraction by Diverging Lens

### Image Formation by convex Lenses

 Position of the object Position of the image Relative size of the image Nature of the image At infinity At focus F2 Highly diminished, point-sized Real and inverted Beyond 2F1 Between F2 and 2F2 Diminished Real and inverted At 2F1 At 2F2 Same size Real and inverted Between F1 and 2F1 Beyond 2F2 Enlarged Real and inverted At focus F1 At infinity Infinitely large or highly enlarged Real and inverted Between focus F1and optical centre O On the same side of the lens as the object Enlarged Virtual and erect Position of the object Position of the image Relative size of the image Nature of the image At infinity At focus F1 Highly diminished, point-sized Virtual and erect Between infinity and optical centre O of the lens Between focus F1 and optical centre O Diminished Virtual and erect

## Optical Instruments Physics

• Telescopes and microscopes are the aids to increase the apparent size of objects by increasing visual angle.
• Very distant objects (such as sun and moon), although very big in size appear very small because they subtend very small visual angle at the eye.
• To see them bigger, we cannot decrease their distance.
• But if with the help of proper lenses, a small image of the distant object be formed close to the eye then its image will subtend a large visual angle at the eye and the object will appear large. Telescope is based on this principle.
• Very small objects subtend small visual angle due to their smallness.
• We can increase the visual angle by bringing these objects closer to the eye, but we cannot do so beyond a certain limit (25cm) because then the objects will not be seen distinct.
• If with the help of proper lenses, a large image of small object is formed, then this image will subtend a large visual angle at the eye and the object will appear large. Microscope is based on this principle.

The document Reflection - Physics | General Test Preparation for CUET is a part of the CUET Course General Test Preparation for CUET.
All you need of CUET at this link: CUET

## FAQs on Reflection - Physics - General Test Preparation for CUET

 1. What are the laws of reflection?
Ans. The laws of reflection state that the angle of incidence is equal to the angle of reflection, and the incident ray, reflected ray, and normal to the surface all lie in the same plane.
 2. How does reflection occur in concave and convex mirrors?
Ans. In a concave mirror, reflection occurs when light rays parallel to the principal axis converge to a focal point after reflecting from the mirror's surface. In a convex mirror, reflection occurs when light rays diverge after reflecting from the mirror's surface.
 3. What is refraction at a plane surface?
Ans. Refraction at a plane surface refers to the bending of light as it passes from one medium to another, such as from air to water or from air to glass. This bending occurs due to the change in the speed of light in different mediums.
 4. How is refraction by spherical lenses different from refraction at a plane surface?
Ans. Refraction by spherical lenses involves the bending of light as it passes through a lens, which has curved surfaces. This bending occurs due to the different refractive indices of the lens material. In contrast, refraction at a plane surface occurs when light passes from one medium to another with a different refractive index.
 5. What are optical instruments used for?
Ans. Optical instruments are used for various purposes, such as magnifying objects, correcting vision problems, and conducting scientific experiments. Examples of optical instruments include microscopes, telescopes, cameras, and eyeglasses.

## General Test Preparation for CUET

187 videos|404 docs|867 tests

## General Test Preparation for CUET

187 videos|404 docs|867 tests

### Up next

Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Download free EduRev App
Track your progress, build streaks, highlight & save important lessons and more!
 (Scan QR code)
Related Searches

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

;