Download CBSE Sample Paper 2024-25 for class 12th to 8th

Light Test - 24

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Light Test - 24

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Weekly Quiz Competition

Question 1
1 / -0

Complete the ray diagram.

A

B

C

D
None

Solution

$$i_1 = r_1$$
$$i_2 = r_2$$
Question 2
1 / -0

What is the value of $$A$$?

A
$$2\ m$$

B
$$5\ m$$

C
$$16\ m$$

D
$$12\ m$$

Solution

The image formed by a plane mirror is situated at the same perpendicular distance behind the mirror as the object is in front of it.
If object distance $$=5\ m$$
Image distance $$=5\ m$$
Question 3
1 / -0

Telescope forms

A
Real Image

B
Virtual Image

C
Both A and B

D
Neither A nor B

Solution

The objective lens of telescope forms a real image while eyepiece forms a virtual image. The first lens, called the objective, forms a real image within the focal length of the second lens, which is called the eyepiece. The image of the objective lens serves as the object for the eyepiece, which forms a magnified virtual image that is observed by the eye.
Question 4
1 / -0

Fill in the blank:

________ mirrors are used in roads and driveway.

A
Concave

B
Convex

C
Plane

D
No

Solution

Convex mirrors help in viewing wider area which is not possible with the help of plane and concave mirror. It helps to look over a wide range and thus is helpful in avoiding accident.
Question 5
1 / -0

Find the odd one out:

A
Shaving mirror

B
Dentist mirror

C
Headlight of car

D
Camera

Solution

Spherical mirrors are used as shaving mirror, dentist mirror and reflector in the headlights of the car. Camera, on the other hand, uses convex lens.
Question 6
1 / -0

A virtual image occurs when light rays appear to converge. One example of the formation of a virtual image is

A
placing an object at the centre of curvature of a concave mirror

B
placing an object in between the pole and the focus of a concave mirror

C
Both A and B

D
Neither A nor B

Solution

When an object is placed in between the pole and the focus of a concave mirror, the reflected rays appear to converge at a point behind the mirror. So, a virtual image is formed.
Question 7
1 / -0

When is the virtual image formed?

A
when the rays of light after reflection or refraction appear to meet at a point

B
when the rays of light after reflection or refraction meet at a point

C
when the rays of light after deflection appear to meet at a point

D
when the lens rays after reflection or refraction meet at a point

Solution

Correct answer (a)
Virtual image is formed when the rays of light after reflection or refraction appear to meet at a point.If light rays, after reflection or refraction, actually meets at a point then real image is formed and if they appears to meet virtual image is formed.
For example if a ray of light from the object, parallel to the principal axis, when passes through a concave lens seem to be coming out of its focus but do not actually meet.Hence a virtual image is formed.
Question 8
1 / -0

A person standing at $$3 m$$ distance from a plane flat mirror would see their image at a distance of:

A
$$0.75 m$$

B
$$1.5 m$$

C
$$2.25 m$$

D
$$3 m$$

E
$$6 m$$

Solution

The distance of image from the plane mirror is same as the distance of object (person) from the plane mirror but the image is formed behind the mirror.
$$\therefore$$ $$v = u =3$$ $$m$$
Thus distance between image and the person $$d = u+v = 3+3 = 6$$ $$m$$
Question 9
1 / -0

A persons image appears on the far side of an optical instrument, upside down. What is the optical instrument?

A
Concave mirror

B
Convex mirror

C
Plane mirror

D
Concave lens

E
Convex lens

Solution

Here the image is upside down means inverted so only concave mirror and convex lens create inverted image. But the concave mirror forms the inverted image same side of the object but here image is opposite side of the object. Thus, it should be convex lens.
Question 10
1 / -0

The discovery of Newton's colour disc proves which of the following statement?

A
Light is colourless

B
Light is not colourless

C
Light has only 1 colour

D
Light has only 3 basic colours

Solution

The perception of a picture or a color stays in the human brain for a fraction of a second. Newton's color disk is a mechanical device that rotates an array of colors arranged as petals or gradients around an axis and when the disc rotates fast enough the perception of the color changes to white. This is because white light is nothing but the mixture of light of all wavelengths in the visible range.

Sir Isaac Newton used this device to prove the above assertion that white color is the mixture of all colors.
So Light is not colourless.