Light Test

Result

Light Test - 29

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Weekly Quiz Competition

Question 1
1 / -0

The line NO that is perpendicular to the plane mirror surface and drawn at the point of incidence is called the :

A
reflected ray

B
incident ray

C
normal

D
refracted ray

Solution

The line NO that is perpendicular to the plane mirror surface and drawn at the point of incidence is called the normal.
Question 2
1 / -0

If an incident light ray is reflected back along its original path by a plane mirror, then its angle of incidence is:

A
$$0^o$$

B
$$90^o$$

C
$$45^o$$

D
$$30^o$$

Solution

If an incident light ray is reflected back along its original path by a plane mirror, then its angle of incidence is 0 degrees.

The angle of incidence is the angle that an incident line or ray makes with the line perpendicular to the surface; at the point of incidence. For a ray to trace back its path, the ray has to fall normally onto the surface of reflection.
Question 3
1 / -0

The angle between incident ray and reflected ray is $$60^\circ{}$$. What is the value of angle of incidence?

A
$$30^\circ{}$$

B
$$60^\circ{}$$

C
$$120^\circ{}$$

D
None of the above

Solution

$$i+r=60^{0}$$
From laws of reflection, $$i=r$$
So, $$i+i=60^{0}$$
or, $$2i=60^{0}$$
or, $$i=30^{0}$$
Question 4
1 / -0

The laws of reflection hold good for :

A
plane mirror only

B
concave mirror only

C
convex mirror only

D
all mirrors irrespective of their shape

Solution

We know that from the laws of reflection, the incident ray, the reflected ray, and the normal to the reflecting surface all lie in the same plane. Also, the angle of reflection is equal to the angle of incidence.
The laws of reflection hold good for all reflecting surfaces irrespective of their shapes whether plane or curved.
Question 5
1 / -0

Which of the following statements is correct regarding rods and cones in the human eye?

A
Cones are sensitive to dim light.

B
Cones are sensitive to bright light.

C
Rods are sensitive to bright light and dim light.

D
Rods can sense colour.

Solution

The retina is the back part of the eye that contains the cells that respond to light. These specialized cells are called photoreceptors. There are 2 types of photoreceptors in the retina: rods and cones.
The rods are most sensitive to light intensity changes. They contain only one type of light-sensitive pigment. Rods are not good for color vision. In a dim room, however, we use mainly our rods, but we are color blind. Rods are more numerous than cones in the periphery of the retina. There are about 120 million rods in the human retina.
The cones are less sensitive to light. However, cones are more sensitive to one of three different colors (green, red or blue). Signals from the cones are sent to the brain which then translates these messages into the perception of color. Cones, however, work only in bright light.
Question 6
1 / -0

Two mirrors A and B are placed at right angles to each other as shown in figure. A ray of light incident on mirror A at an angle of $$25^{\circ}$$ falls on mirror B after reflection. The angle of reflection for the ray reflected from mirror B would be :

A
$$25^{\circ}$$

B
$$50^{\circ}$$

C
$$65^{\circ}$$

D
$$115^{\circ}$$

Solution

On plotting the ray diagram, we get by geometry the angle of reflection for the ray reflected from mirror B = $$65^o$$.
Question 7
1 / -0

In above figure, showing the refraction of light by a plane mirror. Which option is correct ?

A
$$x=$$angle of incidence and $$y=$$angle of reflection.

B
$$y=$$angle of incidence and $$y=$$angle of reflection.

C
$$x$$ and $$y$$ are both angle of incidence .

D
$$x$$ and $$y$$ are both angle of reflection.

Solution

The plane mirror will be perpendicular to the normal.
here,$$x=$$the angle of incidence
$$y=$$the angle of reflection
Question 8
1 / -0

Light is falling on surface S$$_{1}$$,S$$_{2}$$,S$$_{3}$$ as shown in the figure. Surfaces on which the angle of incidence is equal to the angle of reflection is/are :

A
S$$_{1}$$ only

B
S$$_{1}$$ and S$$_{2}$$ only

C
S$$_{2}$$ and S$$_{3}$$

D
all the three surfaces

Solution

The laws of reflection hold good for any type of reflection. So, for all the surfaces, the angle of incidence is always equal to the angle of reflection.
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

We can see a non-luminous object when light :

A
emitted by the object falls on the eye

B
is reflected from the object towards our eye

C
completely passes through the object

D
gets completely absorbed by the object

Solution

We know that a non-luminous object is one that does not emit its own light, although it can still reflect light from other sources. So, we can see a non-luminous object, when light is reflected from the object towards our eyes.