Important points that you should remember about the chapter
- Light is a form of energy that enables us to see objects when it gets reflected from them. Light can be detected through our eyes. (Mirror)
- Light travels along a straight line.
- There are two types of images i.e. real images and virtual images.
- The process of changing the path of light through a mirror or shiny object is called the reflection of light.
- There are two types of spherical mirrors i.e. convex mirrors and concave mirrors.
- Lenses are defined as transparent pieces of glass. Lenses are bounded by two spherical surfaces.
- When white light passes through a glass prism then white light gets split into seven colors. This phenomenon of splitting white light is called dispersion of light.
1. Fill in the blanks:
a. An image that cannot be obtained on a screen is called ———-.
Ans: Virtual image.
b. The image formed by a concave ———- is always virtual and smaller in size.
Ans: Mirror.
c. An image formed by a ————- mirror is always of the same size as that of the object.
Ans: Plane.
d. An image that can be obtained on a screen is called a ——— image.
Ans: Real.
e. An image formed by a concave —————- cannot be obtained on a screen.
Ans: Lens.
2. Mark “T” if the statement is true and “F’ if it is false.
a. We can obtain an enlarged and erect image by a convex mirror.
Ans: F.
The convex mirror forms an erect and diminished image.
b. A concave lens always forms a real image.
Ans: F
Concave lenses form virtual, erect and diminished images.
c. We can obtain a real, enlarged and inverted image by a concave mirror.
Ans: T
d. A real image cannot be obtained on the screen.
Ans: F
It is a virtual image that cannot be obtained on the screen.
e. A concave mirror always forms a real image.
Ans: F
Concave mirrors can also form virtual images.
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3. Match the items given in Column I with one or more items in Column II.
| Column I | Column II |
| A plane mirror A convex mirror A convex lens Aconcavemirror A concave lens | used as a magnifying glass. can form images of objects Spread over a large area. used by dentists to see enlarged images of teeth. the image is always inverted and magnified. the image is erect and of the same size as the object. the image is erect and smaller in size than the object. |
Ans: The table showing the matched answers is,
| Column I | Column II |
| A plane mirror | v. the image is erect and of the same size as the object. |
| A convex mirror | ii. can form images of objects Spread over a large area. |
| A convex lens | i. used as a magnifying glass. |
| A concave mirror | iii. used by dentists to see enlarged images of teeth. |
| A concave lens | iv. the image is always inverted and magnified. |
4. State the characteristics of the image formed by a plane mirror.
Ans: Characteristics of the image formed by a plane mirror are:
- The image distance is equal to the object distance.
- Image height is equal to object height.
- The image is virtual and erect.
5. Find out the letters of the English alphabet or any other language known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings.
Ans: A, H, O, T, U, V, W, X, and Y are the letters in the English alphabet which form the same image as the letter is, as they are laterally symmetrical.
6. What is a virtual image? Give one situation where a virtual image is formed.
Ans: Virtual image: When light rays seem to originate at a spot but do not actually intersect, a virtual image is created. It is visible to human eyes. As a result, rear-view mirrors create virtual images.
The situations where a virtual image is formed:
- It is formed when reflected rays appear to meet.
- Such images cannot be obtained on the screen.
- Virtual images are always formed in the plane mirror and convex mirror.
7. State the differences between a convex and a concave lens.
Ans: The difference between convex and concave lens is shown below:
| Convex lens | Concave lens |
| The convex lens is thicker at the middle and thinner at the edges.They can form a real image. | The convex lens is thicker at the middle and thinner at the edges. They can form a real image. |
8. Give one use of a concave and a convex mirror.
Ans: Use of the concave and convex mirror:
- Concave mirror – used as a reflector in a torch.
- Convex mirror – used in vehicles as a rear-view mirror.
9. Which type of lens always forms a real image?
Ans: Neither concave nor convex lenses always form a real image. A convex lens forms both real and virtual images. A concave lens forms virtual, erect and diminished images.
10. Which type of lens always forms a virtual image?
Ans: The type of lens which always forms a virtual image is:
- A concave lens always forms a virtual image.
- After the rays are refracted, they never converge so there will be no real image.
11. A virtual image larger than the object can be produced by a
- Concave lens
- Concave mirror
- Convex lens
- Plane mirror
Ans: (b) Concave mirror.
A concave mirror forms a virtual image larger than the object.
12. David is observing his image in a plane mirror. The distance between the mirror and his image is 4 m. if he moves 1m towards the mirror, then the distance between David and his image will be
- 3 m
- 5 m
- 6 m
- 8 m
Ans: (c) 6 m.
In the above image,
The distance between the mirror and the object is equal to the distance between the mirror and the image.
The distance between the mirror and David’s image is 4m
When he moves 1m towards the mirror, then the distance is reduced as,
The distance between the mirror and the object is 4-1=3m.
Therefore, the distance between David and his image is 3+3=6m.
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13. The rear-view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rear-view mirror the image of a truck parked behind the car. The speed at which the image of the truck appears to approach the driver will be
- 1 m/s
- 2 m/s
- 4 m/s
- 8 m/s.
Ans: (c) 4 m/s.
In a plane mirror, the object and its image always remain at the same distance from the mirror. So, when the car reverses at a speed of 2m/s, then the image will also appear to move towards the driver.
Therefore, the speed at which the image of the truck appears to approach the driver will be 2+2=4m/s.