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 physics reflection of light in spherical mirrors focus and focal length spherical mirror formula and magnification reflection of light by curved surfaces

image of an object approching a convex mirror of radius of curvature 20 m along its optical axis so is observed to move from $\dfrac{25}{3}$ m to $\dfrac{50}{7}$m into 30s. what is the speed of the object in $Km/h$?

  1. $3$
  2. $4$
  3. $5$
  4. $6$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$A=20m$  $f=10m.$

From the mirror equation$:$
$\dfrac{1}{{{v _1}}} + \dfrac{1}{{{u _1}}} = \dfrac{1}{f};$
$\frac{1}{{25/3}} + \dfrac{1}{{{u _1}}} = \dfrac{1}{{10}};$
$ = {u _1} =  - 50\,m.$
furthermore$,$ when the picture of the question is at $50/7m.$
$\dfrac{1}{{{V _2}}} + \dfrac{1}{{{u _2}}} = \dfrac{1}{f}$
$\dfrac{1}{{50/7}} + \dfrac{1}{{{u _2}}} = \dfrac{1}{{10}}$
$ = {u _2} = 25m$
contrast out there of the protest$=50-25=25m$
speed$=$ relocation/time
$=25/30$
$5/6 m/sec$
speed in $km/h$ $ = 5/6 \times 18/5$
$ = 3\,km/h.$
Hence,
option $(A)$ is correct answer.

Multiple choice physics reflection of light in spherical mirrors focus and focal length spherical mirror formula and magnification reflection of light by curved surfaces

A convex mirror of radius of curvature 20 cm forms an image which is half the size of the object.How far is the object from the mirror ?

  1. 5 cm

  2. 7.5 cm

  3. -30 cm

  4. 12.5 cm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Radius of curvature $=20 cm$

So$,$ focal length $=10 cm$
We are given$,$ ${h _o}/2 = {h _i}$
$so,\,{h _o} = 2{h _i}$
$so,\,m = {h _i} = {h _o}$
$m = {h _o}/2{h _o}$
$so,\,m =  - v/u$
$1/2 =  - v/u$
$so,\,u =  - 2v$
By mirror formula$,$ 
$1/f = 1/v + 1/u$
$1/10 = 1/v - \left( { - 1/2v} \right)$
$1/10 = 1/v + 1/2v$
$so,\,1/10 = 2 + 1/2v$
$so,\,1/10 = 3/2v$
$so,\,2v = 30$
$so,\,v = 15\,cm$
$u =  - 2\left( v \right) =  - 30$
Hence,
option $(C)$ is correct answer.

Multiple choice physics reflection of light in spherical mirrors focus and focal length spherical mirror formula and magnification reflection of light by curved surfaces

All the following statements are correct except

  1. The magnification produced by a convex mirror is always less than one.

  2. A virtual, crect , same-size image can be obtained by using a plane mirror.

  3. A virtual, crect , magnified image can be formed by using a convex mirror.

  4. A virtual, inverted , same-sized image can be formed by using a convex mirror.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A convex mirror always forms a virtual, erect, and diminished image for any real object position. Therefore, the magnification is always less than 1. Statement A is correct. Statement D is incorrect because a convex mirror cannot form an inverted image for a real object.

Multiple choice physics reflection of light in spherical mirrors focus and focal length spherical mirror formula and magnification reflection of light by curved surfaces

If a spherical mirror is immersed in a liquid its focal length

  1. Decreases

  2. Remains same

  3. Increases

  4. Increases and Decreases
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The focal length of a spherical mirror depends solely on its radius of curvature and is independent of the medium in which it is placed. Therefore, immersing a spherical mirror in a liquid does not change its focal length, unlike lenses whose focal length depends on refractive indices.

Multiple choice physics reflection of light in spherical mirrors focus and focal length spherical mirror formula and magnification reflection of light by curved surfaces

Magnification produced by a rear view mirror fitted in vehicles

  1. is less than one

  2. is more than one

  3. is equal to one

  4. can be more than or less than one depending upon the position of the object in front of it.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Rear view mirrors in vehicles are convex mirrors. They are designed to provide a wider field of view by forming diminished images, so the magnification is always less than one.

Multiple choice physics reflection of light in spherical mirrors focus and focal length spherical mirror formula and magnification reflection of light by curved surfaces

A concave mirror of radius of curvature 40 cm forms an image of an object placed on the principal axis at a distance 45 cm in front of it. Now if the system (including object) is completely immersed in water $(\mu=1.33)$, then:

  1. the image will shift towards the mirror.

  2. the magnification will reduce.

  3. the image will shift away from the mirror and magnification will increase.

  4. the position of the image and magnification will not change.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Mirror operates on the principle of Laws of reflection. 

Therefore, focal length does not depend upon the medium and object distance is also unchanged, so their will be no change in the image distance, correspondingly magnification will also remain unchanged.

Multiple choice physics reflection of light in spherical mirrors focus and focal length spherical mirror formula and magnification reflection of light by curved surfaces

An object is placed at the centre of curvature of a concave mirror of radius of curvature $20$cm. The nature and position of the image shall be.

  1. Virtual and $15$cm from the mirror
  2. Real and $20$cm from the mirror
  3. Virtual and $20$cm from the mirror
  4. Real and $10$cm from the mirror
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Image of an object placed at center of curvature is inverted, real and of the same size and is formed at the center of curvature. Hence image will be real and at the center of curvature (20 cm from mirror).

Multiple choice physics reflection of light in spherical mirrors focus and focal length spherical mirror formula and magnification reflection of light by curved surfaces

An object is placed at a distance of $50\ cm$ from a convex mirror. A plane mirror is placed in front of the convex mirror in such a way that it covers half of the convex mirror. If the distance between object and plane mirror is $30\ cm$ then there is no parallax between the images formed by two mirrors, the radius of curvature of convex mirror will be :

  1. $50\ cm$
  2. $25\ cm$
  3. $12.5\ cm$
  4. $100\ cm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For the plane mirror, the image is formed 30 cm behind it. For the convex mirror, the object is at 50 cm. No parallax means the images coincide. This setup requires calculating the focal length based on the image position.

Multiple choice physics superposition of waves coherence young's double slit experiment interference

In Lloyd's single mirror method we have

  1. Both sources virtual

  2. One source virtual and one real

  3. Both sources real

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

By reflection we create a virtual source from real source and light from both of these sources are used to create interference pattern in Lloyd's single mirror method.

Multiple choice image formation by lens image formation by lenses ray optics and optical instruments optics physics

If David is observing his image in plane mirror. The distance between the mirror and his image is 4 m. If he moves 1 m towards the mirror, then the distance between David and his image will be :

  1. 3 m

  2. 5 m

  3. 6 m

  4. 8 m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Plane mirror produces erect image and is of same size and also at the same distance from the mirror as the object.

if he moves 1 m, distance of object from mirror= 3 m

distance of image from mirror= 3 m

distance between image and object =6 m.
Multiple choice image formation by lens image formation by lenses ray optics and optical instruments optics physics

When the reflecting or refracting rays do not actually intersect but appear to intersect when produced backwards, 

  1. a real image is formed

  2. a virtual image is formed

  3. either a real or a virtual image is formed

  4. neither a real nor a virtual image is formed
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A virtual image is formed when the refracting or reflecting rays do not actually intersect but appear to intersect when they are produced backwards.

Multiple choice image formation by lens image formation by lenses ray optics and optical instruments optics physics

A real image is formed by

  1. actual intersection of the refracting or reflecting rays

  2. imaginary intersection of the refracting or reflecting rays produced backwards

  3. either actual or imaginary intersection of the reflecting or refracting rays

  4. neither actual nor imaginary intersection of the reflecting or refracting rays
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When the refracting or reflecting rays actually intersect, a real image is formed.