# 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?

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?

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?

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.

(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.

(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)

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