Tag: sign convention for the measurement of distances

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Questions Related to sign convention for the measurement of distances

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

Magnification produced by a convex mirror is $\frac { 1 }{ 3 }$, then distance of the object from mirror is

  1. $\frac { f }{ 3 }$
  2. $\frac { 2f }{ 3 }$
  3. $1f$
  4. $2f$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Magnification m = -v/u = 1/3 for a convex mirror. Using the mirror formula 1/v + 1/u = 1/f, we substitute v = -u/3. This gives -3/u + 1/u = 1/f, leading to -2/u = 1/f, so u = -2f. The distance is 2f.

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 convex lens of focal length 30 cm forms an image of height 2 cm for an object situated at infinity. If a concave lens of focal length 20 cm is placed coaxially at a distance of 26 cm in front of convex lens. then size of final image would be:

  1. $1.25cm$
  2. $2.5 cm$
  3. $2 cm$
  4. $0.75cm$
Reveal answer Fill a bubble to check yourself
B 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

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

The ratio of the size of the image to the size of the object is known as :

  1. the focal plane

  2. the transformation ratio

  3. the efficiency

  4. the magnification ratio
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

magnification ratio is given as:

 size or height of image/ size or height of object
substituted with proper sign convention.

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 40 cm in front of a concave mirror of focal length 20 cm. Determine the ratio of the size of the image and the size of object

  1. 2:1

  2. 1:2

  3. 1:1

  4. 4:1
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Since focal length of concave mirror given is 20cm l. Object is at 40cm distance which means it is at centre of curvature. hence, image will be formed of same size and at centre focus only but real and inverted.