Ray Optics and Optical Test

Result

Ray Optics and Optical Test - 25

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Weekly Quiz Competition

Question 1
1 / -0

The rays parallel and close to the principal axis are called:

A
Converging rays

B
Diverging rays

C
Coherent rays

D
Paraxial rays

Solution

The rays parallel and close to the principal axis are called paraxial rays. The rays parallel but not close to the principal axis are called peripheral rays.
Question 2
1 / -0

A glass slab of thickness 18 cm and refractive index $$\dfrac {3}{2}$$ is placed on a printed matter. The normal shift of the printed matter is:

A
3 cm

B
6 cm

C
9 cm

D
12 cm

Solution

Thickness$$=18 cm$$

Refractive index of glass $$=\dfrac {3}{2}$$

Normal shift of printed matter
$$d=t(1-\dfrac {1}{\mu})$$

$$=18(1-\dfrac {2}{3})$$

$$=6(1)=6cm.$$
Question 3
1 / -0

The distance between the extreme points on the periphery of the mirror is called:

A
focal length

B
radius of curvature

C
principal section

D
none of these

Solution

Principal section is also defined as the normal 'side view' of the mirror for a ray diagram. In the diagram AB is the principal section.
Question 4
1 / -0

The central point of a spherical mirror is called:

A
Pole

B
Centre of sphere

C
Centre of curvature

D
None of these

Solution

The central point of a spherical mirror is called the Pole of the mirror.
Question 5
1 / -0

A plane mirror produces an image that is

A
Real, inverted and larger than the object.

B
Real, upright and same size as the object.

C
Real upright and smaller than the object.

D
Virtual, upright and the same size of the object.

Solution

$$\begin{array}{l}\text { So a plane mirror always forms a virtual, upright } \\\text { and same sized image. }\end{array}$$
Question 6
1 / -0

Refer to the mirror formula, $$\dfrac {1}{v}+\dfrac {1}{u}=\dfrac {1}{f}$$, where the symbols have their usual meanings. Which of the following graphs correctly depicts this variation?

A

B

C

D
None of these

Solution

None of these graphs correctly represents the formula of mirror. With $$\dfrac{1}{u}$$ and $$\dfrac{1}{v}$$ plotted along $$x$$ and $$y$$.
Question 7
1 / -0

One cannot see through fog because:

A
fog absorbs light

B
light is scattered away by the droplets in fog

C
light suffers total internal reflection at the droplets in fog

D
the refractive index of fog is infinity

Solution

One cannot see through fog because light is scattered away by the droplets in fog.
Question 8
1 / -0

Two points such that each focus for the rays proceedings from the other, are called :

A
Centres of curvature

B
Conjugate foci

C
Converging foci

D
None of these

Solution

Conjugate foci are the two points so situated with respect to a converging mirror such that object distance and image distance can be reversible.
Question 9
1 / -0

The angle which subtends the periphery of the spherical mirror at the centre of curvature is called:

A
angular aperture

B
glancing angle

C
critical angle

D
none of these

Solution

distance between extreme points on the periphery of the spherical mirror is called linear aperture and the angle which the periphery of the spherical mirror subtends at the centre of curvature is called angular aperture.
Question 10
1 / -0

A bird is flying 12 m above the surface of pond. The apparent position of the bird as viewed by a fish 1 m below the surface is:
$$\left (\mu _{w}=\frac{4}{3} \right )$$

A
6 m

B
10 m

C
12 m

D
16 m

Solution

Refractive Index of water w.r.t. air, $$\mu_{w,air} = 4/3$$.
So, Refractive Index of air w.r.t. water $$\mu_{air,w}= 3/4$$
Actual height of the bird $$h= 12\ m$$
Let apparent height be x

$$3/4 =$$ real height / apparent height $$= 12/x$$
$$x = 16\ m$$