 # Light - Reflection and Refraction

### Question:

What is the minimum number of rays required for locating the image formed by a concave mirror for an object. Draw a ray diagram to show the formation of a virtual image by a concave mirror. [Delhi] ### Light - Reflection and Refraction

#### Q 1.

Define the focus of a concave mirror. If the radius of curvature of a convex mirror is 30 cm, what would be its focal length? [Foreign]

#### Q 2.

List four properties of the image formed by a plane mirror. [Delhi]

#### Q 3.

What is the nature of the image formed by a concave mirror if the magnification produced by the mirror is +3? [Delhi]

#### Q 4.

Distinguish between a real and a virtual image of an object. What type of image is formed (i) by a plane mirror, (ii) on a cinema screen? [Foreign]

#### Q 5.

A ray of light travelling in air enters obliquely into water. Does the light ray bend towards or away from the normal ? Why? Draw a ray diagram to show the refraction of light in this situation. [Delhi]

#### Q 6.

State the type of mirror preferred as (i) rear view mirror in vehicles, (i0 shaving mirror. Justify your answer giving two reasons in each case.[Delhi] ?

#### Q 7.

The radius of curvature of a spherical mirror is 20 cm. What is its focal length?

#### Q 8.

Draw the following diagram in your answer book and show the formation of image of the object AB with the help of suitable rays. [All India] #### Q 9.

Name the mirror that can give an erect and enlarged image of an object.

#### Q 10.

One  half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.

#### Q 11.

Define ‘refractive index of a transparent medium.’ What is its unit? Which has a higher refractive index, glass or water? [Delhi]

#### Q 12.

To construct a ray diagram, we use two light rays which are so chosen that it is easy to know their directions after reflection from the mirror. List these two rays and state the path of these rays after reflection. Use these rays to locate the image of an object placed between centre of curvature and focus of a concave mirror. [All India]

#### Q 13.

The refractive index of diamond is 2.42. What is the meaning of this statement?

#### Q 14.

A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the lens if the image is equal to the size of the object? Also find the power of the lens.

#### Q 15.

Name the type of mirror used in the following situations.
(b) Side/rear-view mirror of a vehicle
(c) Solar furnace

#### Q 16.

Draw the ray diagram in each case to show the position and nature of the image formed when the object is placed:
(i) at the centre of curvature of a concave mirror
(ii) between the pole P and focus F of a concave mirror
(iii) in front of a convex mirror
(iv) at 2F of a convex lens
(v) in front of a concave lens

#### Q 17.

“The refractive index of diamond is 2.42”. What is the meaning of this statement in relation to speed of light? [Delhi]

#### Q 18.

Define the principal focus of a concave mirror?

#### Q 19.

Define and show on a diagram, the following terms relating to a concave mirror:
(i) Aperture

#### Q 20.

Draw a ray diagram and also state the position, the relative size and the nature of image formed by a concave mirror when the object is placed at the centre of curvature of the mirror. [Delhi]

#### Q 21.

An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image.

#### Q 22.

The refractive indices of four media A, B, C and D are given in the following table: If light, travels from one medium to another, in which case the change in speed will be (i) minimum, (ii) maximum? [Delhi(C)]

#### Q 23.

Redraw the given diagram and show the path of the refracted ray: [All India(C)] #### Q 24.

Redraw the diagram given below in your answer book and show the direction of the light ray after refraction from the lens. [Delhi, All India(C)] #### Q 25.

A concave mirror produces three times magnified (enlarged) real image of object placed at 10 cm in front of it. Where is the image located?

#### Q 26.

The refractive index of glass is 1.50 and the speed of light in air is 3 x 108 ms-1. Calculate the speed of light in glass. [Foreign]

#### Q 27.

Find the focal length of a convex mirror whose radius of curvature is 32 cm.

#### Q 28.

The magnification produced by a plane mirror is +1. What does this mean?

#### Q 29.

A ray of light enters a rectangular glass slab of refractive index 1.5. It is found that the ray emerges from the opposite face of the slab without being displaced. If its speed in air is 3 x 108 ms-1 then what is its speed in glass? [Foreign]

#### Q 30.

(a) With the help of a ray diagram explain why a concave lens diverges the rays of a parallel beam of light.
(b) A 2.0 cm tall object is placed perpendicular to the principal axis of a concave lens of focal length 15 cm. At what distance from the lens, should the object be placed so that it forms an image 10 cm from the lens? Also find the nature and the size of image formed. [Foreign]

#### Q 31.

What is the minimum number of rays required for locating the image formed by a concave mirror for an object. Draw a ray diagram to show the formation of a virtual image by a concave mirror. [Delhi]

#### Q 32.

The refractive index of water is 1.33 and the speed of light in air is 3 x 108 ms-1. Calculate the speed of light in water. [Foreign]

#### Q 33.

(a) “The refractive index of diamond is 2.42”. What is the meaning of this statement?
(b) Name a liquid whose mass density is less than that of water but it is optically denser than water. [Delhi]

#### Q 34.

Which kind of mirrors are used in the headlights of a motor-car and why? [Foreign]

#### Q 35.

Redraw the diagram given below in your answer book and show the direction of the light ray after reflection from the mirror. [Delhi (C)] #### Q 36.

Between which two points related to a concave mirror should an object be placed to obtain on a screen an image twice the size of the object? [All India]

#### Q 37.

Define one dioptre of power of a lens?

#### Q 38.

How should a ray of light be incident on a rectangular glass slab so that it comes out from the opposite side of the slab without being displaced?  [Foreign]

#### Q 39.

Explain why a ray of light passing through the centre of curvature of a concave mirror, gets reflected along the same path. [Delhi]

#### Q 40.

Redraw the diagram given below in your answer book and show the direction of the light ray after refraction from the lens. [All India (C)] #### Q 41.

An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the ¡mage.

#### Q 42.

Find the focal length of a lens of power -2.0 D. What type of lens is this?

#### Q 43.

A girl was playing with a thin beam of light from her laser torch by directing it from different directions on a convex lens held vertically. She was surprised to see that in a particular direction the beam of light continues to move along the same direction after passing through the lens. State the reason for this observation. [Foreign]

#### Q 44.

State the two laws of reflection of light. [Delhi]

#### Q 45.

An object is placed between infinity and the pole of a convex mirror. Draw a ray diagram and also state the position, the relative size and the nature of the image formed. [All India]

#### Q 46.

A ray of light, incident obliquely on a face of a rectangular glass slab placed in air, emerges from the opposite face parallel to the incident ray. State two factors on which the lateral displacement of the emergent ray depends. [Foreign]

#### Q 47.

Redraw the diagram given below in your answer book and show the direction of the light ray after reflection from the mirror. [Delhi (C)] #### Q 48.

Find the power of a concave lens of focal length 2 m.

#### Q 49.

How far should an object be placed from a .convex lens of focal length 20 cm to obtain its image at a distance of 30 cm from the lens? What will be the height of the image if the object is 6 cm tall? [All India]

#### Q 50.

Why do we prefer a convex mirror as a rear-view mirror in vehicles?