Exercises

A. Choose the correct option.

1. A mirror that always produces a virtual, upright image of the same size as the object is a

a. spherical mirror b. convex mirror c. plane mirror d. concave mirror

Answer. c. Plane mirror

2. A convex mirror produces

a.  real and upright image b. real and enlarged images c. virtual and diminished images

d. virtual and enlarged images

Answer. c. Virtual and diminished images

3. A magnifying glass is a

a. convex mirror b. convex lens c. concave mirror    d. concave lenses

Answer. b. Convex lens

4. Car wing mirrors are

a. concave mirrors   b. convex mirrors   c. plane mirrors d. concave lenses

Answer.b. Convex mirrors

B. Fill in the blanks with the correct words.

1. An image that cannot be formed on a screen is called a ……(real/virtual) image

An image that cannot be formed on a screen is called a virtual image.

2. An image that can be formed on a ……………… (mirror/screen) is called a real image

An image that can be formed on a screen is called a real image.

3. A……. …………. (convex/concave) mirror always forms diminished, virtual images.

A convex mirror always forms diminished, virtual images.

4. A…(convex/concave) lens bulges in the middle and is thinner as the edges

A convex lens bulges in the middle and is thinner at the edges.

 5. White light is made of ……(one/many) colour/s

White light is made of many colours.

C Write T for true and F for false. Usually light travels in straight lines.

1.  Usually light travels in straight lines.

2 A rough surface reflects a parallel beam of light in a single direction.

3. A virtual image can be formed on a screen or be touched.

 4. In a concave mirror the reflecting surface is the inner surface of the sphere.

5. Concave lenses are used to make reading glasses.

1.Usually, light travels in straight lines. – T

2. A rough surface reflects a parallel beam of light in a single direction. – F

3. A virtual image can be formed on a screen or be touched. – F

4. In a concave mirror, the reflecting surface is the inner surface of the sphere. – T

5. Concave lenses are used to make reading glasses. – T

D. Answer the following questions:

Q1. Can we see a source of light through a bent tube? Explain your answer.

1.  No, we cannot see a source of light through a bent tube.
2. Light travels in a straight line (this is called the rectilinear propagation of light).
3. Since the tube is bent, the light cannot pass through it in a straight path, making it impossible to see the source.

Q 2. Write down the characteristics of images formed by a plane mirror.

1. The image is virtual (cannot be captured on a screen).
2. It is upright and of the same size as the object.
3. The image is laterally inverted (left appears right and vice versa).
4. The distance of the image from the mirror is equal to the distance of the object from the mirror.

3. Differentiate between real and virtual images.

Real Image	Virtual Image
Can be formed on a screen.	Cannot be formed on a screen.
Formed when light rays actually meet.	Formed when light rays appear to meet.
Inverted (upside down).	Upright (same orientation as the object).
Example: Image formed by a concave mirror.	Example: Image in a plane mirror.

4. Write down three uses of curved mirrors.

1.  Concave mirrors are used in dentist’s mirrors to give a magnified view of teeth.
2.  Convex mirrors are used as side mirrors in cars as they provide a wide field of view.
3. Concave mirrors are used in reflecting telescopes to focus light and magnify distant objects.

5. Why are concave mirrors used as dentist’s mirrors?

1. A concave mirror produces a magnified and upright image when the object is close to it.
2. This helps dentists to see a clear and enlarged view of the teeth for better examination.

6. Would you use a convex or a concave lens if you want to focus the Sun’s rays to a point?

1. A convex lens is used to focus the Sun’s rays to a point.
2. It converges light rays to a single point, which can even cause paper to burn when placed at the focal point.

7. How can we make a band of colours from white light? What is this band of colours called?

1. We can make a band of colours from white light by passing it through a glass prism.
2. The prism splits white light into seven colours: Violet, Indigo, Blue, Green, Yellow, Orange, and Red (VIBGYOR).
3. This band of colours is called the spectrum.

8. Explain an activity to show how we can make a coloured disc white.

1. Take a circular cardboard disc and divide it into seven sections.
2. Colour each section with the seven colours of the spectrum (VIBGYOR).
3. Attach the disc to a stick or a spinning device and spin it very fast.
4. As it spins, the colours mix, and the disc appears white.
5. This happens because of the persistence of vision and the combination of all colours forming white light.