Question 1

Find the size, nature and position of image formed when an object of size  1cm  is placed at a distance of  15\ cm  from a concave mirror of focal length  10cm ?

Accepted Answer

u=-15 cm f=-10 cm h=1 cmFrom mirror formula \dfrac{1}{f}=\dfrac{1}{u}+\dfrac{1}{v} \dfrac{1}{v}=\dfrac{1}{f}-\dfrac{1}{u} \dfrac{1}{v}=\dfrac{1}{-10}-\dfrac{1}{-15} v=-30 cmThe image is formed at a distance  30 cm on the left side of the mirror from the pole. m=\dfrac{h'}{h}=\dfrac{-v}{u} h'=-1	imes \dfrac{-30}{-15} h=-2 cmThe image size is  2 cm and it is real and inverted.

Question 2

An object is placed at (i)  10\ cm , (ii)  5\ cm  in front of a concave mirror of radius of curvature  15\ cm . Find the position, nature and magnification of the image in each case.

Accepted Answer

(a) In concave mirror, using sign convention

u=-10\,cm

R=-15\,cm

f=\dfrac{-15}{2}\,cm

Using mirror’s relation

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

\dfrac{1}{v}=\dfrac{1}{f}-\dfrac{1}{u}

\dfrac{1}{v}=-\dfrac{2}{15}+\dfrac{1}{10}

\dfrac{1}{v}=\dfrac{-1}{30}

v=-30\,cm

Image is real and it forms at a distance of 30 cm in front
of mirror.

Magnification

m=\dfrac{-v}{u}

m=\dfrac{30}{-10}=-3

This shows image is inverted and 3 times magnified.

(b) again using sign convention

u=-5\,cm

f=\dfrac{-15}{2}\,cm

\dfrac{1}{v}=\dfrac{1}{f}-\dfrac{1}{u}

\dfrac{1}{v}=\dfrac{1}{15}

v=+15\,cm

Image is formed at a distance of 15 cm behind the mirror.

Magnification

m=\dfrac{-v}{u}

=\dfrac{-15}{-5}

=3

+3 magnification shows
image is virtual and erect.

Question 3

(a) Draw ray - diagrams to show the formation of images when the object is placed in front of a concave mirror (converging mirror):
(i) between its pole and focus
(ii) between its centre of curvature and focus. Describe the nature, size and position of the image formed in each case.
(b) State one use of concave mirror based on the formation of images as in case (z) above.

Accepted Answer

(i) When an object is placed between the pole and focus of a concave mirror, the image is formed behind the mirror, it is virtual, erect and larger than the object.(ii) When the object is placed between center of curvature and principal focus of a concave mirror the image formed is beyond C  and it is real, inverted and magnified.b. For the first case it is used as shaving mirror.      For the second case it is are useful tools for determining the location of an        image as produced by a concave mirror.

Question 4

You are provided with a concave mirror, a convex mirror, a Concave lens and a convex lens. To obtain an enlarged image of an object you can use either

Accepted Answer

The correct answer is option (b), Concave mirror or convex lens. Enlarged images are formed by only concave mirror or convex lens.

Question 5

We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.

Accepted Answer

Object distance should be
less than the focal length for the formation of an erect image. Hence, the
range of distance of object from the mirror should be less than 15 cm i.e. from
0 to 15 cm in the front of mirror from the pole. The nature of image so formed
will be virtual and erect. The size of the image will be larger than
object. Ray diagram is attached as image to the question.

Question 6

State two differences between a convex and a concave lens.

Accepted Answer

Convex lensConcave lens1.Convex lens can form both real and virtual images.Concave lens always forms a virtual image.2.It can form magnified image.Image is always diminished in size.

Question 7

In torches, search lights and headlights of vehicles the bulb is placed:

Accepted Answer

In torches, search lights and headlights of vehicles the bulb is placed very near to the focus of the reflector to get a parallel beam of light through which we can see to a longer distance.

Question 8

Which of the following can make a parallel beam of light when light from a point source is incident on it?

Accepted Answer

When light rays from a point source is incident on concave mirror and convex lens, emergent beams are parallel and the image is formed at infinity.Convex mirror and concave lens on the other hand always form a virtual image. Emergent beams from these are not parallel but diverging when the object is kept at focus.

Question 9

A student wants to project the image of a candle flame on a screen $80 c m$ in front of a mirror by keeping the candle flame at a distance of $20 c m$ from its pole.
i) Which type of mirror should the student use?
ii) Find the magnification of the image produced.
iii) Find the distance between the object and its image.
iv) Draw a ray diagram to show the image formation in this case and mark the distance between the object and its image.

Accepted Answer

\dfrac {1}{v}+\dfrac {1}{u}=\dfrac {1}{f} \Rightarrow \ \dfrac {1}{-80}+\dfrac {1}{-20}=\dfrac {1}{f} \Rightarrow \ f=\dfrac {20	imes 80}{-(20+80)}=\dfrac {-1600}{100}=-16\ cm i)\   Since ,  f  is negative , the mirror is concave mirror ii)\   Magnification  =\dfrac {-v}{u}=\dfrac {-(-80)}{-20}= 4 ii)\   From figure the distance between object and image is  60\ cm iv)\   Drawn above

Question 10

The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?

Accepted Answer

When the position of object is between the pole of mirror and its principal focus, the image formed by a concave mirror is observed to be virtual, erect and larger than the object.

Parts of Spherical Mirrors

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Important Questions

Find the size, nature and position of image formed when an object of size $1 c m$ is placed at a distance of $15 c m$ from a concave mirror of focal length $10 c m$ ?

An object is placed at (i) $10 c m$ , (ii) $5 c m$ in front of a concave mirror of radius of curvature $15 c m$ . Find the position, nature and magnification of the image in each case.

You are provided with a concave mirror, a convex mirror, a Concave lens and a convex lens. To obtain an enlarged image of an object you can use either

State two differences between a convex and a concave lens.

In torches, search lights and headlights of vehicles the bulb is placed:

Which of the following can make a parallel beam of light when light from a point source is incident on it?

The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?

Parts of Spherical Mirrors

Language

Rate

NEXT VIDEOS

REVISE WITH CONCEPTS

Basic Terms Related to Image Formation by Spherical Mirror

Terms Related To Spherical Mirrors

QUICK SUMMARY WITH STORIES

Terms Related to Spherical Mirror

Basic Terms Related to Spherical Mirrors

Important Questions

Find the size, nature and position of image formed when an object of size 1cm is placed at a distance of 15 cm from a concave mirror of focal length 10cm?

An object is placed at (i) 10 cm, (ii) 5 cm in front of a concave mirror of radius of curvature 15 cm. Find the position, nature and magnification of the image in each case.

You are provided with a concave mirror, a convex mirror, a Concave lens and a convex lens. To obtain an enlarged image of an object you can use either

State two differences between a convex and a concave lens.

In torches, search lights and headlights of vehicles the bulb is placed:

Which of the following can make a parallel beam of light when light from a point source is incident on it?

The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?

Find the size, nature and position of image formed when an object of size $1 c m$ is placed at a distance of $15 c m$ from a concave mirror of focal length $10 c m$ ?

An object is placed at (i) $10 c m$ , (ii) $5 c m$ in front of a concave mirror of radius of curvature $15 c m$ . Find the position, nature and magnification of the image in each case.