Physics

Light and Mirrors

454 Questions

Light and mirrors questions cover the principles of reflection, image formation, and mirror magnification. Concepts include the properties of plane mirrors, the uses of concave mirrors in solar devices, and the behavior of light rays. These fundamentals are essential general science topics in major competitive examinations.

Plane mirror propertiesConcave mirror applicationsMirror magnification formulaLight reflection lawsImage formation

Light and Mirrors Questions

Multiple choice evs light, shadows and images what makes things visible nature and sources of light light travels in straight line

Which of the following statements is true?

  1. The image formed by a pinhole camera is inverted because light travels in a straight line.

  2. Light does not change its direction on reflection.

  3. As we move the object away from the light source, the shadow of the object becomes smaller.

  4. Reflection is possible only from polished surface.

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Light changes its direction after reflection. As we move the object away from the light source, the shadow becomes larger as the distance between object and the light source increases. Reflection is possible from rough surface also.

Multiple choice physics universe and space xx radio telescope and space telescopes optical instruments : telescope

The Hubble Space Telescope is designed with ____________  hyperbolic mirrors is known for good imaging performance over a wide field of view. 

  1. two

  2. four

  3. three

  4. many

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hubble space telescope is reflecting telescope it is designed with TWO hyperbolic mirrors. A curved primary mirror is the basic optical element that creates an image at the focal plane. And secondary mirror was added to modify the optical characteristics for visual observation.

Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

The object distance $u$ for a concave mirror:

  1. must be positive

  2. must be negative

  3. must not be negative

  4. may be negative

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Positive and negative sign depend on the assumption of sign conversion.
either side we can consider positive or negative.
Hence Option D.

Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

The linear magnification for a mirror is the ratio of the size of the image to the size of the object, and is denoted by m. Then m is equal to (symbols have their usual meanings).

  1. $\displaystyle \frac { uf }{ u-f } $
  2. $\displaystyle \frac { uf }{ u+f } $
  3. $\displaystyle \frac { f }{ u-f } $
  4. None of these

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

we now,$\dfrac{1}{f}=\dfrac{1}{v}+\dfrac{1}{u}$
multiplying by u in above eq.
$\dfrac{u}{f}=\dfrac{u}{v}+\dfrac{u}{u}$
$\dfrac{u}{f}=\dfrac{u}{v}+1$
$\dfrac{u}{f}-1=\dfrac{u}{v}$
$\dfrac{u}{v}=\dfrac{u-f}{f}$
$\dfrac{v}{u}=\dfrac{f}{u-f}  ,  As, m=\dfrac{v}{u}$
$m=\dfrac{f}{u-f}$
hence,option C is correct.

Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

The sum of the reciprocals of object distance and image distance is equal to the __________ of a mirror.

  1. focal length

  2. reciprocal of the focal length

  3. radius of curvature

  4. reciprocal of the radius of curvature

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The sum of the reciprocals of object distance and image distance is equal to the reciprocal of the focal length of a mirror.

Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

The relation between $u,\,v\;and\;f$ for a mirror is given by

  1. $f=\displaystyle\frac{u\times v}{u-v}$
  2. $f=\displaystyle\frac{2u\times v}{u+v}$
  3. $f=\displaystyle\frac{u\times v}{u+v}$
  4. $f=\displaystyle\frac{u-v}{u+v}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The relation between $u,\,v\;and\;f$ for a mirror is given by $f=\displaystyle\frac{u\times v}{u+v}$

Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

Choose the correct relation between $u,\,v\;and\;r$ for a spherical mirror, where $r$ is radius of curvature.

  1. $r=\displaystyle\frac{2uv}{u+v}$
  2. $r=\displaystyle\frac{2}{u+v}$
  3. $r=\displaystyle\frac{2(u+v)}{(uv)}$
  4. $r=\displaystyle\frac{2uv}{u-v}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The relation between $u,\,v\;and\;f$ for a mirror is given by $f=\displaystyle\frac{u\times v}{u+v}$

so $r=\displaystyle\frac{2u\times v}{u+v}$

Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

State whether true or false : 

The magnification produced by a spherical mirror is the ratio of the height of the image to the height of the object.

  1. True

  2. False

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The magnification is the ratio of height of the image to height of the object. The image is smaller than the object, the magnification will be less than 1. If the image if upside down (inverted) then magnification will be negative.

Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

A concave mirror forms an erect image of an object placed at a distance of 10 cm from it. The size of the image is double that of the object. Where is the image formed?

  1. 20 cm behind the mirror

  2. 20 cm in front of the mirror

  3. 40 cm behind the mirror

  4. 40 cm in front of the mirror

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Since the image is erect , so the magnification ratio must be positive .


$m=2$

also $u=-10cm$

so $m=-\dfrac{v}{u}$

$2=-\dfrac{v}{-10}$ 

$v=20cm$

So the image is virtual and 20 cm from mirror on the other side of the object.

Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

A dentist wants a small mirror that when placed $2$cm from a tooth, will produce $3\times$ upright image. What kind of mirror must be used and what must its focal length be?

  1. Concave mirror, $3.04$ cm
  2. Concave mirror, $1.5$ cm
  3. Convex mirror, $3.0$ cm
  4. Convex mirror, $1.5$cm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$m=+\dfrac{v}{u}=\dfrac{+f}{u-f}$
$3=\dfrac{+f}{+2+f}\Rightarrow f=3cm$.

Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

When a ray of light parallel to the principle axis is incident on a concave mirror$,$ the reflected ray

  1. Passes through C

  2. Passes through F

  3. Passes midway between P and F

  4. retraces its path

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

By definition, rays incident parallel to the principal axis of a concave mirror reflect through the principal focus (F).

Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

A mirror faces the negative x-axis. (Normal to its reflecting surface is$- \hat { i } )$  While a particle starts moving such that its image is formed in the mirror. At a certain instant the velocity of the particles is $3 \hat { i } + 4 \hat { j } + 5 \hat { k }$ and that of the mirror is $\hat { 1 } - \hat { j } + \hat { k }$ Choose the correct options.

  1. Magnitude of relative velocity of the image w.r.t mirrror is$\sqrt { 45 }$
  2. Magnitude of relative velocity of image w.r.t object is 4

  3. Magnitude of relative velocity of image w.r.t mirrror is $\sqrt { 45 }$
  4. Absolute velocity of the image w.r.t ground is$\sqrt { 42 }$
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

$\begin{array}{l} In\, y-direction \ { V _{ o } }={ V _{ i } } \ \Rightarrow { V _{ i } }=4\widehat { j }  \ In\, z-direction \ { V _{ i } }={ V _{ o } } \ \Rightarrow { V _{ i } }=5\widehat { k }  \ In\, x-direction \ { V _{ IM } }=-{ V _{ oM } } \ \Rightarrow { V _{ IM } }=-{ V _{ oM } } \ \Rightarrow { V _{ I } }-{ V _{ M } }={ V _{ M } }-{ V _{ o } } \ \Rightarrow { V _{ I } }=2{ V _{ M } }-{ V _{ o } } \ =2\left[ { \widehat { i }  } \right] -3\left[ { \widehat { i }  } \right]  \ =-\widehat { i }  \ \therefore \overrightarrow { { V _{ I } } } =-\widehat { i } +4\widehat { j } +5\widehat { k }  \ \therefore \overrightarrow { { V _{ iM } } } =-2\widehat { i } +5\widehat { j } +4\widehat { k }  \ \therefore \left| { \overrightarrow { { V _{ iM } } }  } \right| =\sqrt { 45 }  \end{array}$

Hence,
option $(A)$ and $(C)$ are both correct answer.

Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

A small candle 2.5 cm in size is placed 27 cm in front of a concave mirror of radius of curvature 36 cm.

  1. The distance from the mirror, should a screen be placed in order to receive a sharp image is-54 cm.

  2. The nature of image is virtual inverted w.r.t. object.

  3. The image formed is 8 times highest the object.

  4. The image formed is 3 times highest the object.

Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics reflection of light in spherical mirrors sign convention for mirrors sign convention for spherical mirrors sign convention for the measurement of distances

An object is placed at a distance of 36 cm from a convex mirror . A plane mirror is placed in between , so that the two virtual image so formed coincide . If the plane mirror is at a distance of 24 cm from the object , find the radius of curvature of the convex mirror . 

  1. $43 cm$
  2. $36 cm$
  3. $78 cm$
  4. $97 cm$
Reveal answer Fill a bubble to check yourself
B Correct answer