Physics (Std XII) - atomic energy central school no:4,rawatbhata

Atomic Energy Central School No. 4, Rawatbhata
Physics (Std XII)
Chapter - Nine
RAY OPTICS & OPTICAL INSTRUMENTS
VSA [1 MKS]
Q1.A converging lens is kept coaxially in contact with a diverging lens both the lenses being of equal focal lengths.
what is the focal length of the combination ?
[Or]
A convex lens of focal length f1 is kept in contact with a concave lens of focal length f2 Find the focal length of the
combination.
Q2.When light travels from a rarer to a denser medium, the speed decreases. Does this decrease in speed imply a
decrease in the energy carried by the light wave? Justify your answer.
Q3.For the same value of angle of incidence, the angles of refraction in three media A, B and C are 150, 250 and 350
respectively. in which medium would the velocity of light be minimum ?
Q4.A biconvex lens mode of a transparent material of refractive index 1.25 is immersed in water of refractive index
1.33. Will the behave as a converging or a diverging lens? Give reason.
VSA [2 MKS]
Q5. An object AB is kept in front of concave mirror as shown in the figure.
(i) Complete the ray diagram showing the image formation of the object.
(ii)How will the position and intensity of the image be affected if the lower half of the mirror's reflecting?
Surface is painted black?
Q6 .Draw a labeled ray diagram of a reflecting telescope. Mention its two advantages over the refracting telescope.
Q7. Suppose that the lower half of the concave mirror’s reflecting surface is covered with an opaque (nonreflective) material. What effect will this have on the image of an object placed in front of the mirror?
Q8 .Two monochromatic rays of light are incident normally on the face AB of an isosceles right-angled prism ABC.
The refractive indices of the glass prism for the two rays ‘1’and ‘2’ are respectively 1.35 and 1.45 trace the path of
these rays after entering through the prism.
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Q9.Two monochromatic rays of light are incident normally on the face AB of an isosceles right-angled prism ABC.
the refractive indices of the glass prism for the two rays ‘1’and ‘2’ are respectively 1.3 and 1.5 trace the path of these
rays after entering through the prism.
Q10 Two monochromatic rays of light are incident normally on the face AB of an isosceles right-angled prism ABC.
the refractive indices of the glass prism for the rays ‘1’ and’2’ are respectively 1.38 and 1.52.trace the path of these
rays after entering though the prism.
Picture
VSA [3 MKS]
Q11. (i) Draw a neat labeled ray diagram of an astronomical telescope in normal adjustment. Explain briefly its
working.
(ii) An astronomical telescope uses two lenses of powers 10 D and .1D What is its magnifying power in normal
adjustment?
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Q12.(i) draw a neat labeled ray Diagram of a compound microscope .explain briefly its working.
(ii) Why must both the objective and eye-piece of a compound microscope have short focal lengths?
Q13.The image obtained with a convex lens is erect and its length is four times the length of the object and image
distances. If the focal length of the lens is 20 cm, then find the object distance and image distance .
Q14.A convex lens made up of glass of refractive index 1.5 is dipped, in turn, in (i) a medium of refractive index
1.65,(ii) a medium of refractive index 1.33.
(a)Will it behave as converging or a diverging lens in the two cases.
(b)How will its focal length change in the two media. ?
Q15.Use the mirror equation to show that an object placed between f and 2f a concave mirror produces a real image
beyond 2f.(a)A convex mirror always produces a virtual image independent of the location of the object.
(b )An object placed between the pole and focus of a concave mirror produces a virtual and enlarged image.
Q16.A compound microscope uses an objective lens of focal length 4 cm and eyepieces lens of focal length 10cm. an
object is placed at 6 cm from the objective lens .Calculate the magnifying power of the compound microscope. Also
calculate the length of the microscope.
Q17.A giant refracting telescope at an observatory has an objective lens of focal length 15 m. If an eyepiece lens of
length 1.0cm is used, find the angular magnification of the telescope. If this telescope is used to view the moon,
image of the moon formed by the objective lens ? The diameter of the moon is 3.42 x 106 m and the radius of the
lunar orbit is 3.8 x108 m.
Q18.You are given three lines L1,L2 andL3 each of focal length 20cm.An object is kept at 40cm in front of L1 as
shown. The final real image is formed at the focus ‘I’ as shown the final real image is formed at the focus ‘I’ of L3
Find the separation between L1, L2 and L3.
Q19.A convex lens of focal length 20 cm is placed coaxially with a convex mirror of radius of curvature 20cm.the two
are kept at 15cm from each other. A point object lies 60cm in front of the convex lens. Draw a ray diagram to show
the formation of the image by the combination. Determine the nature and position of the image formed.
Q20.A biconvex lens made of a transparent material of refractive index 1.5 cm is immersed in water of refractive
index 1.33.Will the lens behaves as a converging or a diverging lens? GIVE reason.
Q21.A Convex lens of focal length 20cm is placed coaxially with a concave mirror of focal length 10cm at a distance
of 50 cm apart from each other. A beam of light coming parallel to the principal axes is incident on the convex lens.
Find the position of the final image forced by this combination. Draw the ray diagram showing the formation of the
image.
Q22.A biconcave lens made of a transparent material of refractive index 1.25 is immersed in water of refractive
index1.33. Will the lens behave as a converging or a diverging lens? Give reason.
[
Q23. A Convex lens of focal length 20cm is placed coaxially with a convex mirror of radius of curvature 20cm.the
two are kept 15cm apart. A point object is placed 40cm in front of the convex lens. Find the position of the image
formed by this combination. Draw the ray diagram showing the image formation.
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Chapter Ten- WAVE OPTICS
VSA [1 MKS]
Q1. How does the angular separation between fringes in single-slit diffraction experiment change
when the distance of separation between the slit and screen is doubled ?
VSA [2 MKS]
Q2.A parallel beam of light of 450 nm falls on a narrow slit the resulting diffraction pattern is
observed on a screen 1.5 m away. it is observed that the first minimum is at a distance of 3 mm
from the centre of the screen. Calculate the width of the slit.
VSA [3 MKS]
Q3 .In young’s double slit experiment, the two slit 0.12 mm apart are illuminated by
monochromatic light of wavelength 420 nm. the screen is 1.0m away from the slit.
find the distance of the second (i) bright fringe,(ii) dark fringe from the central maximum. How will
the fringe pattern change if the screen is moved away from the slits ?
Q4.(a) What is linearly polarized light ?Describe briefly using a diagram how sunlight is polarized.
(b) Unpolarised light is incident on a Polaroid. How would the intensity of transmitted light change
when the Polaroid is rotated ?
Q5.(a)Using the phenomenon of polarization, show how transverse nature of light can be
demonstrated.(b)Two Polaroid P1 and P2 are Placed with their pass axes perpendicular to each
other. Unpolarised light of intensity i0 is incident on p1 A third Polaroid P3 is kept in between P1 and
P2 such that its pass axis makes an angle of 300 with that of P1 Determine the intensity of light
transmitted though P1,P2andP3.
VSA [5 MKS]
Q6.State the importance of coherent sources in the phenomenon of interference.
In young’s double alit experiment to produce interference pattern, obtain the conditions for
constructive and destructive interferences.
Hence does the fringe width get affected, if the entire experimental apparatus of young is
immersed in water?
Q7.(a) State Huygens’ principle. Using this principle explain how a diffraction pattern is obtained
on a screen due to a narrow slit on which a narrow beam coming from a monochromatic source
of light is incident normally
(b)Show that the angular width of the first diffraction fringe is half of that of the central fringe.
(c) If a monochromatic source of light is replaced by white light, What change would you
observe in the diffraction pattern ?
Q8. (a) In young’s double slit experiment, derive the condition for (i) constructive interference
(ii)destructive interference at a point on the screen.
(b) A beam of light consisting of two wavelengths,800 nm and 600 nm is used to obtain the
interference fringes in a young’s double slit experiment on by 0.28 mm, calculate the least
distance from the center bright maximum where the fringes of the two wavelengths coincide.
Q9.(a) how does an unpolarized light incident on a Polaroid get polarized ?Describe briefly, with
the help of a necessary diagram, the polarization of light by reflection from a transparent medium.
(b) Two Polaroid ‘A’ and ‘B’ are kept in crossed position. How should a third Polaroid ‘C’ be placed
between them so that the intensity of polarized light transmitted by Polaroid B reduces to 1/8th of
the intensity of unpolarized on A ?
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Q10(a)In young’s double slit experiment, describe Briefly how bright and dark friar obtained on the
Screen kept in front of a double slit. Hence obtain the expression for the fringe width.
(b)The ratio of the intensities at minima to the maxima in the young’s double slit experiment is 9:25.
Find the ratio of the widths of the slits.
Q11.(a) Describe briefly how a diffraction pattern is obtained on a screen due to a single narrow
slit illuminated by a monochromatic source of light. Hence obtain the conditions for the angular
width of secondary maxima and secondary minima.
(b)Two wavelengths of sodium light of 590 nm and 596 nm are used in true to study the diffraction
taking place at a single slit of aperture 2 X 10-6 m. the distance between the position of first
maxima of the diffraction pattern obtained in the two cases.
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