EASY
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Where should an object 6 cm long be placed in front of a convex mirror of focal length 60 cm to obtain an image 2 cm long.

Important Questions on Ray Optics and Optical Instruments

EASY

A mirror is placed at an angled of 30° with respect to y-axis (see figure). A light ray travelling in the negative y-direction strikes the mirror. The direction of the reflected ray is given by the vector

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MEDIUM
A flat mirror revolves at a constant angular velocity making n=0.4 revolutions per second. With what velocity (in m s-1) will a light spot move along a spherical screen with a radius of 15 m, if the mirror is at the centre of curvature of the screen?
HARD
A ray of light, travelling in the direction 12i^+3 j^, is incident on a plane mirror. After reflection, it travels along the direction 12i^-3 j^. The angle of incidence is
HARD

A hemispherical glass body of radius 10 cm and refractive index 1.5 is silvered on its curved surface. A small air bubble is 6 cm below the flat surface inside it along the axis. The position of the image of the air bubble made by the mirror is seen :

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MEDIUM
Match the corresponding entries of column 1 with column 2. [Where m is the magnification produced by the mirror]
  Column 1   Column 2
(A) m=-2 (a) Convex mirror
(B) m=-12 (b) Concave mirror
(C) m=+2 (c) Real image
(D) m=+12 (d) Virtual image
HARD
A concave mirror of radius of curvature R has a circular outline of radius r. A circular disc is to be placed normal to the axis at the focus so that it collects all the light that is reflected from the mirror from a beam parallel to the axis. For rR , the area of this disc has to be at least
MEDIUM
In a car a rear view mirror having a radius of curvature 1.50 m forms a virtual image of a bus located 10.0 m from the mirror. The factor by which the mirror magnifies the size of the bus is close to
MEDIUM

A point object is moving uniformly towards the pole of a concave mirror of focal length 25 cm along its axis as shown below. The speed of the object is 1 ms-1. At t=0, the distance of the object from the mirror is 50 cm. The average velocity of the image formed by the mirror between time t=0 and t=0.25 s is:

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MEDIUM

A point source of light, S is placed at a distance L in front of the center of plane mirror of width d which is hanging vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror, at a distance 2L as shown below. The distance over which the man can see the image of the light source in the mirror is:

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MEDIUM
You are asked to design a shaving mirror assuming that a person keeps it at 10 cm from his face and views the magnified image of the face at the closest comfortable distance of 25 cm. The radius of curvature of the mirror would then be:
MEDIUM
To find the focal length of a convex mirror, a student records the following data:
Object pin Convex Lens Convex Mirror Image Pin
22.2 cm 32.2 cm 45.8 cm 71.2 cm
The focal length of the convex lens is f1 and that of mirror is f2 . Then taking index correction to be negligibly small, f1 and f2 are close to:
MEDIUM

A particle is oscillating on the x-axis with an amplitude 2 cm about the point x0=10 cm with a frequency. A concave mirror of focal length 5 cm is placed at the origin (see figure).

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Identify the correct statements?
(i) The image executes periodic motion.
(ii) The image executes non-periodic motion.
(iii) The turning points of the image are asymmetric with respect to the image of the point at X=10 cm.
(iv) The distance between the turning points of the oscillation of the image is 10021 cm.

HARD
A concave mirror has radius of curvature of 40 cm. It is at the bottom of a glass that has water filled up to 5 cm (see figure). If a small particle is floating on the surface of water, its image as seen, from directly above the glass, is at a distance d from the surface of water. The value of d is close to: (Refractive index of water =1.33)
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EASY
A beam of light from a source L is incident normally on a plane mirror fixed at a certain distance x from the source. The beam is reflected back as a spot on a scale placed just above the source L. When the mirror is rotated through a small angle θ, the spot of the light is found to move through a distance y on the scale. The angle θ is given by
MEDIUM
A concave mirror for face viewing has a focal length of 0.4 m. The distance at which you hold the mirror from your face in order to see your image upright with a magnification of 5 is
MEDIUM
When an object is kept at a distance of 30 cm from a concave mirror, the image is formed at a distance of 10 cm from the mirror. If the object is moved with a speed of 9 cm s-1 , the speed (in cm s-1) with which image moves at that instant is
EASY
A concave mirror of focal length 15 cm, forms an image having twice the linear dimensions of the object. The position of the object, when the image is virtual, will be
MEDIUM
A 1 cm height needle is placed at a distance of 0.1 m from a convex mirror of focal length 0.05 m, then size of the image is
MEDIUM
Two plane mirrors are inclined to each other such that a ray of light incident on the first mirror M1 and parallel to the second mirror (M2) is finally reflected from the second mirror (M2) and parallel to the first mirror M1. The angle between the two mirrors will be:
MEDIUM
An object is placed at a distance of 40 cm from a concave mirror of focal length 15 cm. If the object is displaced through a distance of 20 cm towards the mirror, the displacement of the image will be