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Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics option c: imaging the mirror formula derivation of formula for curved mirrors mirror formula and magnification

In case of a virtual and erect image, the magnification created by the mirror is

  1. positive

  2. negative

  3. unity

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

Magnifaction of a mirror is defined as
$m=\dfrac{size of image}{size of object}$
and since, in case of virtual and errect image, size of image and object both are positive  . Hence magnification created by mirror is positive.

Multiple choice physics option c: imaging the mirror formula derivation of formula for curved mirrors mirror formula and magnification

In case of a real and inverted image, the magnification created by the mirror is

  1. positive

  2. negative

  3. unity

  4. infinity
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Magnification of image created by mirror is defined as
$m=\dfrac{size of image}{size of object}$
and in case of inverted image. Size of image is negative whereas size of object is positive. Hence , magnification produced is negative and it can be unity when object is placed at center of curvature and infinity when object is at focus.

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

What is the formula for spherical mirrors for object distance p and image distance q ?

  1. $\dfrac{1}{p}+q=\dfrac{1}{f}$

  2. $\dfrac{1}{p}+\dfrac{1}{q}=\dfrac{1}{f}$

  3. $\dfrac{1}{p}+\dfrac{1}{q}=f$

  4. $p+\dfrac{1}{q}=\dfrac{1}{f}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Mirror formula is given as: 
$ \dfrac{2}{R} = \dfrac{1}{v} + \dfrac{1}{u} $

where, $ R $ is the radius of curvature of the spherical mirror
$u $ is the object distance from the pole
$ v $ is the image distance from the pole

We know,
$ f = \dfrac{R}{2} $

$ \Rightarrow \dfrac{1}{f} = \dfrac{1}{v} + \dfrac{1}{u} $

$ \therefore $ For object distance $ p $ and image distance $ q $, mirror formula becomes
$ \dfrac{1}{f} = \dfrac{1}{p} + \dfrac{1}{q} $

Hence, the correct answer is OPTION B.
Multiple choice physics reflection of light at curved surfaces the mirror formula derivation of formula for curved mirrors mirror formula and magnification

A plane mirror produces an image that is

  1. Real, inverted and larger than the object.

  2. Real, upright and same size as the object.

  3. Real upright and smaller than the object.

  4. Virtual, upright and the same size of the object.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A plane mirror always forms a virtual, upright image that is the same size as the object, located at the same distance behind the mirror as the object is in front.

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

A point object is placed at a distance $10cm$ and its real image is formed at a distance of $20cm$ from concave mirror. If the object is moved by $0.1cm$ towards the mirror, the image will shift by about

  1. $0.4cm$ away from the mirror

  2. $0.4cm$ towards the mirror

  3. $0.8cm$ away from the mirror

  4. $0.8cm$ towards the mirror
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$We\quad know\quad \dfrac { 1 }{ f } =\dfrac { 1 }{ u } +\dfrac { 1 }{ v } ;\quad \ where\quad f=focal\quad length=?\ u=\quad initial\quad distance=20\quad cm\ v=\quad final\quad distance=10cm\ \dfrac { 1 }{ f } =\dfrac { 1 }{ -20 } +\dfrac { 1 }{ (-10) } \ f=\dfrac { 20 }{ 3 } \quad cm\ Now\quad object\quad moved\quad towards\quad the\quad mirror=0.1\quad cm,so\quad the\quad new\quad value\quad of\quad u=9.9\quad cm\ Again\quad \quad \quad \ \dfrac { 1 }{ f } =\dfrac { 1 }{ { u } _{ 1 } } +\dfrac { 1 }{ { v } _{ 1 } } \ \dfrac { 1 }{ f } -\dfrac { 1 }{ { u } _{ 1 } } =\dfrac { 1 }{ { v } _{ 1 } } \ \dfrac { 1 }{ { v } _{ 1 } } =\quad \dfrac { 3 }{ 20 } -\dfrac { 1 }{ (-9.9) } \ { v } _{ 1 }=20.4\quad cm\ The\quad change\quad in\quad final\quad distance\quad =20.4cm\quad -20\quad cm=0.4\quad cm\ \ v=\dfrac { 9\times 1600 }{ 3600 } =\quad 4cm/s$

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

A plane mirror produces a magnification of

  1. $-1$

  2. $+1$

  3. Zero

  4. infinity
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The magnification produced by a plane mirror is $+1$ implies that the image formed by a plane mirror is virtual$,$

erect and of the same size$,$ as that of object$.$
Hence,
option $(B)$ is correct answer.

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

If two mirrors are inclined at some angle $\theta$. An object is placed between the mirrors and there are 5 images formed for an object, then $\theta$ is may be

  1. $45^o$

  2. $53^o$

  3. $63^o$

  4. $75^o$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The number of images formed by two mirrors at an angle $\theta $ is

$\begin{array}{l} n=\dfrac { { 360 } }{ \theta  } -1 \ \because n=5\, \, \left( { given } \right)  \ \therefore 5=\dfrac { { 360 } }{ \theta  } -1 \ \therefore \theta =\dfrac { { 360 } }{ 6 } ={ 60^{ 0 } } \end{array}$
Hence, the angle may be $63^0$.

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

The relation between $u, v$ ( u is the object distance and v is the image distance )  and f for mirror is given by:

  1. $\displaystyle f=\frac{uv}{u-v}$

  2. $\displaystyle f=\frac{2u\times v}{u+v}$

  3. $\displaystyle f=\frac{u\times v}{u+v}$

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\dfrac{1}{u} +\dfrac{1}{v} = \dfrac{1}{f} $

or $\dfrac{u+v}{uv} = \dfrac{1}{f}$
or $f=\dfrac{uv}{u+v}$