Light Reflection and Refraction Test

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Light Reflection and Refraction Test - 35

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Weekly Quiz Competition

Question 1
1 / -0

The centre of curvature of a ______ mirror lies behind the mirror.

A
Convex

B
Concave

C
Both $$A$$ and $$B$$

D
None of these

Solution

The centre of curvature of a convex mirror is behind it. In the image C is the centre of curvature.
Question 2
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 3
1 / -0

The unit of magnification is:

A
m

B
$$m^2$$

C
$$m^{-1}$$

D
None of these

Solution

Magnification is define as ratio of image height to object height.
$$M=\dfrac{h_i}{h_o}$$

Units, Unit of height is 'meter (m)'

$$[M]=\dfrac{[h_i]}{[h_o]}=\dfrac mm$$

Hence dimensionless

Option B
Question 4
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 5
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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 6
1 / -0

The centre of curvature of a ___________ mirror is in front of it.

A
convex

B
concave

C
convex or concave

D
none of these

Solution

The centre of curvature of a concave mirror is in front of it. In the image c is the centre of curvature.
Question 7
1 / -0

Which of the following quantity does not have any unit?

A
Velocity of light

B
Light year

C
Magnification

D
Power of a lens

Solution

Magnification does not have any unit as it is the ratio of same quantity.
Question 8
1 / -0

In a concave mirror, an object is placed a distance $$d_1$$ from the focus and the real image is formed at a distance $$d_2$$ from the focus. Then the focal length of the mirror is

A
$$\sqrt {d_1d_2}$$

B
$$d_1d_2$$

C
$$\frac {d_1d_2}{2}$$

D
$$\sqrt {d_1/d_2}$$

Solution

Given: In a concave mirror, an object is placed a distance $$d_1$$ from the focus and the real image is formed at a distance $$d_2$$ from the focus.
To find the focal length of the mirror
Solution:
Let the focal length of the concave mirror be $$f$$
And as the image formed is real, the object distance and image distance have same sign convention.
According to the given criteria,
Object distance, $$u=f+d_1$$
Image distance, $$v=f+d_2$$
Now by applying mirror formula, we get
$$\dfrac 1f=\dfrac 1v+\dfrac 1u\\\implies \dfrac 1f=\dfrac {v+u}{vu}\\\implies vu=f(v+u)$$
Substituting the values of $$v$$ and $$u$$, we get
$$(f+d_2)(f+d_1)=f(f+d_2+f+d_1)\\\implies f^2+fd_1+fd_2+d_1d_2=2f^2+fd_1+fd_2\\\implies 2f^2-f^2=d_1d_2\\\implies f^2=d_1d_2\\\implies f=\sqrt{d_1d_2}$$
is the required focal length of the concave mirror.
Question 9
1 / -0

A glass slab is placed in the path of a beam of convergent light; the point of convergence of light

A
Moves towards the glass slab

B
Moves away from the glass slab

C
Remains at the same point

D
Undergoes a lateral shift

Solution

As seen in ray diagram given ,if a glass slab is placed in the path of a beam of convergent light; the point of convergence of light moves away from the glass slab in the direction of light.
Question 10
1 / -0

A lens which is thinner at the middle and thicker at the edges is called a :

A
Convex lens

B
Concave lens

C
Cylindrical lens

D
None of these

Solution

A lens which is thinner at the middle and thicker at the edges is called a concave lens.