Light Reflection and Refraction Test

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Light Reflection and Refraction Test - 33

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Weekly Quiz Competition

Question 1
1 / -0

The imaginary line passing through the pole and the center of curvature of the curved mirror is called its _______.

A
Focal length

B
Radius of curvature

C
Principal axis

D
None

Solution

The imaginary line passing through the pole and the center of curvature of the curved mirror is called its principal axis.
Question 2
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A convex mirror has a focal length f. A real object is placed at a distance f/2 in front of it from the pole. The mirror produces an image at

A
$$3f$$

B
$$f$$

C
$$2f$$

D
$$f/3$$

Solution

Given,
Focal length $$=f$$
Object distance $$u=-\dfrac f2$$
Lens formula,
$$\displaystyle \cfrac{1}{v} - \cfrac{1}{u} =\dfrac{1}{f}$$

$$\displaystyle \cfrac{1}{v} - \cfrac{2}{f} =\dfrac{1}{f}$$

$$\cfrac{1}{v} =\cfrac{-3}{f}$$

$$v=\cfrac{f}{3}$$
Option D
Question 3
1 / -0

The point F is the :

A
Principal axis

B
Principal focus

C
Pole

D
None

Solution

Point F is called the principal focus where parallel light rays after reflection meet.
Question 4
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A beam of light is incident through the holes on side A and emerges out of the holes on the other face of the box as shown in the fogure. Which of the following could be inside the box ?

A
Concave lens

B
Rectangular glass slab

C
Prism

D
Convex lens

Solution

Answer is D.

A convex lens is a converging lens. When parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus. A convex lens is thicker at the center.
In this case, as the rays meet at the focus and then spread out in opposite direction, a convex lens is present inside the box.
Question 5
1 / -0

Which of the following statements are always true?

A
(i) and (ii) only

B
(ii) and (iii) only

C
(i) and (iii) only

D
(i), (ii) and (iii)

Solution

Rays coming from an object at infinity converge at the focus of the converging lens.

As the object approaches the lens, the image size increases. When the object is placed at the focus, a real image of a much larger size than the object is formed at the infinity.

When an object is placed between the focus and optical centre, a magnified virtual image is formed.

Hence, all the three statements are True.
Question 6
1 / -0

Which is the path of rays of light when it enters with oblique incidence from water into air ?

A

B

C

D

Solution

According to law of refraction if a ray of light travels from denser to rarer medium it bends away from normal from its original path.
(considering water as denser than air)
Question 7
1 / -0

The path of a ray of light passing through a rectangular glass slab tested by four students are shown in the figure as $$ A, B, C,$$ and $$D $$. Which one of them is correct?

A
$$A$$

B
$$B$$

C
$$C$$

D
$$D$$

Solution

According to the law of refraction if a ray travels from rarer to denser medium the ray of light bends towards the normal and when a ray travels from denser to rarer medium the ray of light bends away from the normal. Case A, C, and D do not follow the law of refraction but case B does.
Question 8
1 / -0

A student focussed the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle screen and the lens as under :

Position of candle $$= 12.0\ cm$$
Position of convex lens $$= 50.0\ cm$$
Position of the screen $$= 88.0\ cm$$

What will be the nature of the image formed if he further shifts the candle towards the lens?

A
Virtual and erect

B
Real and inverted

C
Real and diminished

D
None of the above

Solution

Before shifting the candle,

$$u=12-50=-38cm$$

$$v=88-50=38cm$$

$$\cfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$$

$$\cfrac{1}{f}=\dfrac{1}{38}+\dfrac{1}{38}$$

$$\cfrac{1}{f}=\dfrac{1+1}{38}$$

$$f=19\ cm$$

Hence, before shifting the candle, it is placed at a distance of $$2f$$ from the mirror.

When candle is shifted towards the lens from this position, its distance from the lens is $$f<u<2f$$. In this scenario, image formed is virtual, diminished and erect.
Question 9
1 / -0

A small hole P is made in a piece of cardboard. The hole is illuminated by a torch as shown in Fig. 16.3. The pencil of light coming out of the hole falls on a mirror.
At which point should the eye be placed so that the hole can be seen?

A
A

B
B

C
C

D
D

Solution

According to law of reflection we know in case of plane mirror the angle of reflection is equal to the angle of incidence. So,if we place the eye on point $$A$$ the hole can be seen.
Question 10
1 / -0

In case of a real and inverted image, the magnification of a mirror is:

A
Positive

B
Negative

C
Zero

D
Infinity

Solution

We know,
Magnification(M)$$=\dfrac{height \ of\ image({h}_{i})}{height\ of \ object({h}_{o})}$$

Here, image is inverted so according to sign convention $$height \ of \ image({h}_{i})$$will be negative while object height will be positive.
Hence, the magnification of a mirror is negative.