NCERT Science Class 10 Chapter 10 Light-Reflection and Refraction CBSE Board Sample Problems Very Short Answer

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Question

Define one dioptre of power of a lens?

Solution

Power of a lens is one dioptre if focal length of a lens is 1 m.

Question

Name the kind of surfaces that

(i) Reflect

(ii) Refract most of the light falling on them.

Solution

(i) Optically Plane surface

(ii) Transparent surface

Question

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

Solution

Concave mirror

Question

What is the angle of incidence and angle of reflection when light is falling normally on concave mirror?

Solution

Both the angles will be 0

Question

Name any two factors on which lateral displacement in case of a glass slab depends.

Solution

Angle on incidence

Thickness of the glass slab

Question

The magnification produced by a mirror is -1. What is your conclusion by the nature of mirror used and the position of the object?

Solution

Concave mirror and the object is at C

Question

What is the minimum distance between the object and its real image in case of a concave mirror?

Solution

Zero

Question

In which direction, a ray of light bends when it goes from water to glass?

Solution

It will bend towards the normal.

Question

An object is placed 80 cm from converging lens of focal length 25 cm. What is the nature of image?

Solution

The image is real, inverted and diminished as the object is placed beyond 2F.

Question

Under what conditions a lens becomes invisible when placed in a transparent liquid?

Solution

This happens when refractive index of the lens becomes equal to that of liquid

Question

Refractive index of two material mediums X and Y are 1 .3 and 1.5 respectively. In which of the two, the light would travel faster?

Solution

In medium X because of lower value of refractive index.

Question

Between which two points of a concave mirror should an object be placed to obtain a virtual magnified image?

Solution

Between F and P.

Question

A man standing in front of a spherical mirror, finds his image having a very small head, a fat body and legs of normal size. What types of mirrors are used in this part?

Solution

A very small head: convex mirror

A fat body: concave mirror, and

Legs of normal size: plane mirror

Question

The following questions consists of two statements - Assertion (A) and Reason (R).

Answer these questions selecting the appropriate option given below:

(a) Both A and R are true and R is correct explanation of A.

(b) Both A and R are true and R is not correct explanation of A.

(c) A is true but R is false.

(d) A is false but R is true

Assertion (A): Refractive index have no units.

Reason (R): the refractive index is ratio of two similar quantities.

Solution

(a)

Question

The following questions consists of two statements — Assertion (A) and Reason (R).

Answer these questions selecting the appropriate option given below:

(a) Both A and R are true and R is correct explanation of A.

(b) Both A and R are true and R is not correct explanation of A.

(c) A is true but R is false.

(d) A is false but R is true

Assertion (A): A convex mirror is used as a rear view/driver’s mirror.

Reason (R): convex mirror have a wider field of view as they are curved outwards.

They also give an erect, though diminished image.

Solution

(a)

Question

An object 5cm high is placed at a distance 2f from a convex lens. What is the height of the image formed? (1)

Solution

The height of image=height of the object= 5cm. (1)