# Light - Reflection and Refraction

### Question:

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]

Along the normal to the surface or at an incident angle of i = 0 °.

### Light - Reflection and Refraction

#### Q 1.

Define one dioptre of power of a lens?

#### Q 2.

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 3.

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 4.

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 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.

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 7.

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

#### Q 8.

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 9.

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 10.

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

#### Q 11.

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

#### Q 12.

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

#### Q 13.

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 14.

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

#### Q 15.

Between which two points of a concave mirror should an object be placed to obtain a magnification of -3? [Delhi]

#### Q 16.

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

#### Q 17.

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

#### Q 18.

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

#### Q 19.

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

#### Q 20.

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 21.

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 22.

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

#### Q 23.

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

#### Q 24.

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

#### Q 25.

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 26.

In an experiment with a rectangular glass slab, a student observed that a ray of light incident at an angle of 55 ° with the normal on one face of the slab, after refraction strikes the opposite face of the slab before emerging out into air making an angle of 40 ° with the normal. Draw a labelled diagram to show the path of this ray. What value would you assign to the angle of refraction and angle of emergence? [All India]

#### Q 27.

(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 28.

List four properties of the image formed by a concave mirror, when object is placed between focus and pole of the mirror. [Delhi]

#### Q 29.

The outer surface of a hollow sphere of aluminium of radius 50 cm is to be used as a mirror. What will be the focal length of this mirror? Which type of spherical mirror will it provide? [Delhi]

#### Q 30.

Define the principal focus of a concave mirror?

#### Q 31.

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 32.

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 33.

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 34.

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 35.

A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed. [Delhi]

#### Q 36.

The image of an object placed at 60 cm in front of a lens is obtained on a screen at a distance of 120 cm from it. Find the focal length of the lens. What would be the height of the image if the object is 5 cm high? [Foreign]

#### Q 37.

An object 5.0 cm in length Is placedat a distanc, of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image nature and size.

#### Q 38.

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 39.

Name the type of mirror used in the following situations:
(i) Headlights of a car (ii) Rear-view mirror of vehicles (iii) Solar furnace Support your answer with reason. [All India][Foreign]

#### Q 40.

An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens. [All India]

#### Q 41.

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

#### Q 42.

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 43.

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

#### Q 44.

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

#### Q 45.

To instruct a ray diagram, we use two light rays which are so chosen that it is easy to know their directions after refraction from the lens. List these two rays and state the path of these rays after refraction. Use these two rays to locate the image of an object placed between â€˜F and ‘2F of a convex lens. [Foreign]

#### Q 46.

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

#### Q 47.

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 48.

At what distance should an object be placed from a convex lens of focal length 18 cm to obtain an image at 24 cm from it on the other side. What will be the magnification produced in this case? [Delhi]

#### 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.

What is understood by lateral displacement of light? Illustrate it with the help of a diagram. List any two factors on which the lateral displacement of a particular substance depends. [Foreign]