Important Questions for Class 10 Science Chapter 10 – Light: Reflection and Refraction

# Important Questions for Class 10 Science Chapter 10 – Light: Reflection and Refraction

Below are some important questions for class 10 science chapter 10 – Light: Reflection and Refraction students must study thoroughly.When light rays bounce off a surface, transition from one transparent medium to another, or move through a medium whose composition is continuously changing, they change direction. This is known as reflection. To understand the images produced by plane and curved mirrors, the law of reflection can be applied.When light travelling through one transparent medium encounters a boundary with another transparent medium, some of the light is reflected, and some is transmitted into the second medium. The transmitted light’s direction changes when it enters the second medium; this is known as refraction.

Some of the important questions topics for class 10 science chapter 10 – Light: Reflection and Refraction are:

• Reflection of Light
• Spherical Mirrors
• Refraction of Light
• Image Formation by Lenses
• Power of a Lens

Below are some of the important questions for class 10 science chapter 10 – Light: Reflection and Refraction from an examination point of view.

## Class 10 Science Important Questions Chapter 10 – Light: Reflection and Refraction

Q1. List four characteristics of the images formed by plane mirrors.

Solution:

Characteristics of the image formed by a plane mirror are

(i) image distance is same as that of object distance

(ii) image formed is virtual and erect

(iii) image formed is of the same size as that of the object

(iv) image formed is laterally inverted (left appears right and right appears left).

Q2. When an object is kept within the focus of a concave mirror, an enlarged image is formed behind the mirror. This image is

(a) real

(b) inverted

(c) virtual and inverted

(d) virtual and erect

Solution:

(d) When an object is placed between the principal focus and pole of a concave mirror, an enlarged virtual and erect image is formed behind the mirror.

Q3. An object is placed at a distance of 12 cm in front of a concave mirror of radius of curvature 30 cm. List four characteristics of the image formed by the mirror.

Solution:

Radius of curvature (R) = 30 cm, object distance is 12 cm in front of the mirror. Thus we can say that object is placed between focus and pole. Four characteristics of the image formed by die given concave mirror when object is placed between pole and focus are:

(i) Virtual

(ii) Erect

(iii) Enlarged

(iv) Image is formed behind the mirror

Q4. Mention the types of mirrors used as (i) rear view mirrors, (ii) shaving mirrors. List two reasons to justify your answer in each case.

Solution:

(i) Convex mirror is used as rear view mirror because

(a) it gives erect image.

(b) it gives diminished image thus provides wider view of traffic behind the vehicle.

(ii) Concave mirror is used as shaving mirror because

(a) it gives erect image when mirror is close to the face.

(b) it gives enlarged image of the face so that a person can shave safely.

Q5. State the types of mirrors used for (i) headlights and (ii) rear view mirrors, in motorcycles. Give reason to justify your answer in each case.

Solution:

(i) Concave mirrors are used in headlights of cars to get powerful beams of light.

(ii) Convex mirrors are used as rear-view mirrors of vehicle to get a wider field of view and and erect image of traffic behind.

Q6. A convex lens of focal length 20 cm can produce a magnified virtual as well as real image. Is this a correct statement? If yes, where shall the object be placed in each case for obtaining these images?

Solution:

Yes, it is correct. If the object is placed within 20 cm from the lens in the first case and between 20 cm and 40 cm in the second case.

Q7. What is the angle between the incident ray of light and the emergent ray of light, when incident ray of light falls obliquely on the glass slab ?

Solution:

When incident ray of light falls obliquely on the glass slab, then the emergent ray of light is parallel to the incident ray of light. Therefore, angle between the incident and emergent rays of light is zero.

A ray of light falls obliquely on the glass slab. The perpendicular distance between the emergent ray of light and the original path of the incident ray is 2 mm.

Q8. An object is placed at the following distances from a concave mirror of focal length 15 cm.

(a) 10 cm

(b) 20 cm

(c) 30 cm

(d) 40 cm

Which position of the object will produce

• Virtual image
• A diminished real image
• An enlarged real image
• An image of same size

Solution:

• Concave mirror forms virtual image if object is placed between the focus and pole of the mirror. Therefore, for the position of object at 10 cm mirror forms the required image.
• A real and diminished image is formed when object lies beyond C i.e. beyond 2F. So, for the position of object at 40 cm, mirror forms the required image.
• An enlarged real image is formed when object lies between F and 2 F. So, for the position of object at 20 cm, mirror forms the required image.
• An image of same size of the object is formed when object lies at C or 2F. So, for the position of object at 30 cm, mirror forms the required image.

Q9. Identify the nature of the mirror and mention two characteristics of the image formed when magnification (m) = + 6.

Solution:

m = + 6 means size of image formed = 6 times the size of the object and the image is erect. Such image is formed by a concave mirror when object is placed between the focus and pole of the mirror. The image is virtual and magnified.

Q10. How can you identify the three types of mirrors without touching ?

Solution:

We can identify the three types of mirrors by looking at them. If the size of the image of an object is of the same size as that of the object, then mirror is plane mirror. If the size of the image of an object increases as the object is brought closer to the mirror and the size of image is highly magnified when the object is very close to the mirror, then the mirror is concave mirror. If the size of the image is smaller and full length of the image of an object is seen, then the mirror is convex mirror.