Tag: reflection of light at curved surfaces

Questions Related to reflection of light at curved surfaces

The concave mirrors are used in:

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

  1. Reflecting telescope

  2. Magic-lanterns

  3. Cinema projectors

  4. All of these

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Correct Option: D
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.

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

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

  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

Show answer
Correct Option: B,C
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.

___________ are used in telescopes to reflect light.

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

  1. Concave mirrors

  2. Convex mirrors

  3. Plane mirrors

  4. Convex lenses

Show answer
Correct Option: A
Explanation:

Concave mirrors are used in telescope to reflect light.


Answer-(A).

The light emanating from a torchlight is

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

  1. Convergent

  2. Divergent

  3. Parallel

  4. Irregular

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Correct Option: B
Explanation:

A torch has a bulb working on a battery. A bulb spreads its light rays in all directions. Thus it always diverges.

Mirror used by a dental surgeon is ___________.

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

  1. Plane

  2. Convex

  3. Concave

  4. Convex and concave

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Correct Option: C
Explanation:

The concave mirror is used by the dentist as the image formed by the concave mirror when placed between pole and focus is magnified and erect and it provides a clear image to repair tooth cavities.

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

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

  1. 1 m

  2. 0.5 m

  3. 0.24 m

  4. 2 m

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Correct Option: C
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 $(C)$

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?

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

  1. +0.23

  2. -0.23

  3. +0.45

  4. -0.45

Show answer
Correct Option: A
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 
$=-\dfrac{v}{u}=-\dfrac{1.15}{-5}=0.23$

What is known as linear magnification of spherical mirrors?

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

  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

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Correct Option: A
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.

Magnification $(m) =$ ______

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

  1. $\dfrac {v}{u}$

  2. $\dfrac {u}{v}$

  3. $\dfrac {h _{o}}{h _{i}}$

  4. $\dfrac {h _{i}}{h _{o}}$

Show answer
Correct Option: D
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.

For magnification in spherical mirrors object height is :

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

  1. Negative.

  2. Positive.

  3. For real images positive.

  4. For virtual images negative.

Show answer
Correct Option: B
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.