Tag: physics

Questions Related to physics

What will be the height of image when an object of $2\ mm$ is placed at a distance $20 \ cm$ infront of the axis of a convex mirror of radius of curvature $40\ cm$ ?

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

  1. $20\ mm$

  2. $10\ mm$

  3. $6\ mm$

  4. $1\ mm$

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Correct Option: D
Explanation:

$\begin{array}{l} \dfrac { 1 }{ V } +\dfrac { 1 }{ \mu  } =\dfrac { 1 }{ f }  \ \dfrac { 1 }{ V } =\dfrac { 1 }{ { 10 } } ,V=10cm \end{array}$

Height of object
$\begin{array}{l} =2mm=\dfrac { 1 }{ 5 } cm \ \dfrac { { Hi } }{ { Ho } } =\dfrac { V }{ 4 }  \ \dfrac { { Hi } }{ { 1/5 } } =\dfrac { { 10 } }{ { -20 } } \Rightarrow Hi=-\dfrac { 1 }{ { 10 } }  \ 1mm\, \, above\, \, axis \end{array}$

A convexo-concave diverging lens is made of glass of refractive index 1.5 and focal length 24 cm. Radius of curvature for one surface is doubled that of the other. Then radii of curvature for the two surface are (in cm) :

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

  1. 6 , 12

  2. 12, 24

  3. 3, 6

  4. 18, 36

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Correct Option: D

An object is placed at 15 cm from a convex lens of focal length 10 cm . Where should another convex mirror of radius 12 cm placed such that image will coincide with object

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

  1. 18 cm

  2. 17 cm

  3. 14 cm

  4. 20 cm

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Correct Option: A

Your are asked to design shaving mirror assuming that a person keep it 10 cm from his face and views the magnified image of the face at the closest comfortable distance of 25 cm. the reduice of curvature of the mirror would then be 

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

  1. 24 cm

  2. 60 cm

  3. -24 cm

  4. 30 cm

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Correct Option: A

A spherical surface of radius of curvature $R$ separates air (refractive index 1.0) from glass (refractive index 1.5).The centre of curvature is in the glass. A point object $P$ placed in air is found to have a real image $Q$ in the glass. The line $PQ$ cuts the surface at a point $\mathbf { O } \text { and } \mathbf { P O }= \mathrm { OQ }$.Find the distance of object from the spherical surface.

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

  1. 3R

  2. 5R

  3. R

  4. 2R

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Correct Option: A

A $10\mathrm { mm }$ long awl pin is placed vertically In front of a concave mirror. A $5\ mm$ long image of the awl pin is formed at $30\mathrm { cm }$ in front of the mirror, The focal length of this mirror is 

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

  1. $- 30 \mathrm { cm }$

  2. $- 20 \mathrm { cm }$

  3. $- 40 \mathrm { cm }$

  4. $- 60 \mathrm { cm }$

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Correct Option: B

A point object is placed on principal axis of concave mirror of radius of curvature 10 cm at a distance 21 cm from pole of the mirror.  A glass slab of thickness 3 cm and refractive index 1.5 is placed between object and mirror $.$ Find the imaged position of the image formed. 

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

  1. 4

  2. 3

  3. 16.5

  4. 5

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Correct Option: C

A converging bundle of light rays in the shape of cone with a vertex angle of 45 falls on a circular diaphragm of 20 cm diameter. A lens with power 5 D is fixed in the diaphragm. Diameter of face of lens is equal to that of diaphragm. If the vertex angle of new cone is 

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

  1. $
    \cfrac { 3 d } { 4 }
    $

  2. $
    \cfrac { 5 d } { 4 }
    $

  3. $
    2 d
    $

  4. $
    \cfrac { 3 } { 2 } d
    $

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Correct Option: B

All the following statements are correct except

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

  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.

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Correct Option: A

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

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

  1. Decreases

  2. Remains same

  3. Increases

  4. Increases and Decreases

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Correct Option: C