Tag: reflection of light at curved surfaces

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Questions Related to reflection of light at curved surfaces

Multiple choice physics reflection of light at curved surfaces uses of curved mirrors uses of spherical mirror uses of spherical mirrors

The concave mirrors are used in:

  1. Reflecting telescope

  2. Magic-lanterns

  3. Cinema projectors

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A reflecting telescope uses concave mirrors as they produce images similar to the images produced by convex lenses i.e. upright and smaller than the object.

The magic lantern used a concave mirror in back of a light source to direct as much of the light as possible through a small rectangular sheet of glass.

Concave mirrors project a beam of light outward, which is required in a cinema projector.

Multiple choice physics reflection of light at curved surfaces uses of curved mirrors uses of spherical mirror uses of spherical mirrors

A concave mirror forms an image of the sun at a distance of 12 cm from it. Then:

  1. the radius of curvature of this mirror is 6 cm

  2. to use it as a shaving mirror, it can be held at a distance of 8-10 cm from the face

  3. if an object is kept at a distance of 24 cm from it, the image formed will be of the same size as the object

  4. all the above alternatives are correct
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

Concave mirror forms an image of the sun at a distance of 12 cm.
So the focal length of mirror is 12 cm.
Radius of mirror is $f \times 2=24cm$
For shaving we need to get a virtual image which should be magnified and erect.
So the mirror must be kept at a reasonable distance of 8-10 cm which is within focus and pole.
As the radius is 24cm the object placed at center forms image at the same place
Options $B,C$ are correct.

Multiple choice physics reflection of light at curved surfaces problems on mirror and magnification formula derivation of formula for curved mirrors mirror formula and magnification

An object is placed at a distance of 1.5 m from a screen and a convex lens is interposed between them. The magnification produced is 4. The focal length of the lens is then

  1. 1 m

  2. 0.5 m

  3. 0.24 m

  4. 2 m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Here, $m =\dfrac{v}{u} =-4$

$\Rightarrow u = \dfrac{-v}{4}$------------(1)

Also, $|u| + |v| = 1.5$

$\dfrac{v}{4} + v = 1.5$

$\Rightarrow \dfrac{(v+4 v)}{4} = 1.5$

 $\Rightarrow  v = 1.2 m$

So, putting the value of $v$ in equation (1):
 $u= \dfrac{-1.2}{4} = -0.3 m\,\,\,$

$\therefore  f =\dfrac{uv}{u-v}$

$\Rightarrow f=\dfrac{(-0.3 \times 1.2)}{(-0.3 - 1.2)} = 0.24m$
Hence the correct option is $(C)$

Multiple choice physics reflection of light at curved surfaces problems on mirror and magnification formula derivation of formula for curved mirrors mirror formula and magnification

A convex mirror used for rear view on an automobile has a radius of curvature of 3.00m. If a bus is located at 5.00m from this mirror, find magnification?

  1. +0.23

  2. -0.23

  3. +0.45

  4. -0.45
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\dfrac{2}{R}=\dfrac{1}{u}+\dfrac{1}{v}$

$\dfrac{2}{3}=\dfrac{1}{-5}+\dfrac{1}{v}$
$\dfrac{1}{v}=0.866 \Rightarrow  v = 1.15$ cm
Magnification 
$=-\dfrac{v}{u}=-\dfrac{1.15}{-5}=0.23$

Multiple choice physics reflection of light at curved surfaces problems on mirror and magnification formula derivation of formula for curved mirrors mirror formula and magnification

What is known as linear magnification of spherical mirrors?

  1. Ratio of size of image to size of object

  2. Ratio of shape of image to size of object

  3. Ratio of size of image to shape of object

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation


Ratio of size of image to size of object is known as linear magnification of spherical mirrors.

Linear magnification (m) is the ratio of height of image to that of the object.

Multiple choice physics reflection of light at curved surfaces problems on mirror and magnification formula derivation of formula for curved mirrors mirror formula and magnification

Magnification $(m) =$ ______

  1. $\dfrac {v}{u}$
  2. $\dfrac {u}{v}$
  3. $\dfrac {h _{o}}{h _{i}}$
  4. $\dfrac {h _{i}}{h _{o}}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Magnification is ratio of the size of the image $h _i$ to the size of the object $h _o$.

$m=\dfrac{h _i}{h _o} = \dfrac{-v}{u}$ where $u$ is object distance and $v$ is image distance.

Multiple choice physics reflection of light at curved surfaces problems on mirror and magnification formula derivation of formula for curved mirrors mirror formula and magnification

For magnification in spherical mirrors object height is :

  1. Negative.

  2. Positive.

  3. For real images positive.

  4. For virtual images negative.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Magnification is the increase in the image size produced by spherical mirrors with respect to the object size. It is the ratio of the height of the image to the height of the object. The height of the object is always positive as the object is always above the principal axis.