BHARAT INTERNATIONAL SENIOR SECONDARY SCHOOL (CBSE),KRISHNAGIRI.

AFFILIATED TO CBSE NEW DELHI – 1930502

REVISION TEST - I
CLASS : XII MARKS: 70
SUBJECT : PHYSICS DATE:18.08.2023
Instructions
1. This question paper contains 37 questions. Question paper is divided into Five sections - Section A, B,
C, D, and E .
2. Question paper is divided into 5 sections - section A, B, C, D, E,
3. In section A : question no. 1 to 18 are multiple choice type questions carrying 1 mark each.
4. In section B : question no. 19 to 25 are short answer-1 type questions carrying 2 marks each.
5. In section C : Question no. 26 to 31 are short answer -2 type questions carrying 3 marks each.
6. in section D : Question no. 32 to 35 are Long answer type questions carrying 5 marks each .
7. In section E : Question no. 36 and 37 are case -based questions carrying 4 marks each.

SECTION-A 18X 1=18

1. The number of photoelectrons emitted per second from a metal surface increases when
(a) the energy of incident photons increases
(b) the frequency of incident light increases
(c) the wavelength of the incident light increases
(d) the intensity of the incident light increases
2. The maximum kinetic energy of the photoelectrons varies
(a) inversely with the intensity and is independent of the
frequency of the incident radiation
(b) inversely with the frequency and is independent of the intensity of the incident radiation
(c) linearly with the frequency and the intensity of the incident radiation
(d) linearly with the frequency and is independent of the intensity of the incident radiation
3. In a photoelectric experiment, the stopping potential VS, is plotted against the frequency v of incident
light. The resulting curve is a straight line which makes an angle with the v-axis. The tan will be
equal to (  = work function of surface)
(a) h/e (b) e/h (c)-/e (d) eh/
4. The work function for Al, K and Pt is 4.28 eV, 2.30 eV and 5.65 eV respectively. Their respective
threshold frequencies would be
(a) Pt > Al > K (b) Al > Pt>K
(c) K> Al > Pt (d) Al > K > Pt
5. According to Einstein's photoelectric equation, the graph of KE of the photoelectron emitted from
the metal versus the frequency of the incident radiation gives a straight line graph, whose slope
(a) depends on the intensity of the incident radiation
(b) depends on the nature of the metal and also on the intensity of incident radiation
(c) is same for all metals and independent of the intensity of the incident radiation
(d) depends on the nature of the metal
6. Which of the following can form a virtual, erect and magnified image?
(a) Plane mirror (b) Concave mirror
(c) Convex mirror (d) Concave lens
7. If refractive index of glass is 1.50 and of water is 1.33, then critical angle is
−1 8 −1 2
(a) sin (b) sin
9 3
−1 8
(c) cos (d) None of these
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1
8. The divergent lens in m linear magnification produced by the lens is
1 1
(a) m (b) (c) m+1 (d)
m m+1
9. When a ray of light falls on a given plate at an angle of incidence 60°, the reflected and refracted
rays are found to be normal to each other. The refractive index of the material of the plate is
√3
(a) (b) 1.5 (c) 1.732 (d) 2
2
10. The refractive indices of glass and water with respect to air are 3/2 and 4/3 respectively. The
refractive index of glass with respect to water will be
(a) 8/9 (b) 9/8 (c) 7/6 (d) None of these
11. Two incoherent sources of intensities l and 4l superpose, then the resultant intensity is
(a) 5l (b) 9l (c) 3l (d) l
12. Two coherent sources of intensities, l1 and l2 produce an interference pattern. The maximum
intensity in the interference pattern will be
(a) l1 + l2 (b) l12 + l22 (c) (l1 + l2)2 (d) (l1 + l2)2
13. In Young's double slit experiment, instead of taking slits of equal widths, one slit is made twice as
wide as the other.Then, in the interference pattern
(a) the intensities of both the maxima and the minima increase
(b) the intensity of maxima increases and the minima has zero intensity
(c) the intensity of maxima decreases and that of the minima increases
(d) the intensity of maxima decreases and the minima has zero intensity
14. When a thin transparent plate of thickness t and refractive index μ is placed in the path of one of the
two interfering waves of light, then the path difference between two waves is
( µ+1)
(a) (µ +1)t (b) (µ -1)t (c) (d) µt
t
15. In Young's double slit experiment, the fringe width will remain same, if (D= distance between screen
and plane of slits, d = separation between two slits and λ= wavelength of light used)
(a) Both λ and D are doubled
(b) Both d and D are doubled
(c) D is doubled but d is halved
(d) λ is doubled but d is halved

Directions (Q. Nos. 16-18) : These questions consists of two statements each printed as Assertion
and Reason. While answering these questions you are required to choose any one of the following
five responses.
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If Assertion is false but Reason is true.
(e) If both Assertion and Reason are false.
16. Assertion If wavelength is of the order of distance between the slits, then fringe size is large.
Reason Fringe width is given by β = 2D/d.
17. Assertion In Young's double slit experiment, often both the phenomena interference and
diffraction are present.
Reason Diffraction results due to superposition of wavelets from different points of the some
wavefront.
18. Assertion In diffraction phenomenon different maximas have different intensities.
Reason In interference different maximas have same intensities.
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 SECTION-B 7X 2=14
19. Draw a graph between the frequency of incident radiation (v) and the maximum kinetic energy of
the electrons emitted from the surface of a photosensitive material. State clearly how this graph can
be used to determine
(i) Planck’s constant and
(ii) work function of the material.

20. Using the graph shown in the figure for stopping potential versus the incident frequency of photons,
calculate Planck’s constant.

21. State Einstein’s photo electric equation, in terms of frequency and wavelength.
22. What is mirror formula of focal length and give the equation of linear magnification of mirror , in
terms of focal length.
23. Explain the critical angle (i.e ) when light goes from denser medium to rarer medium.
24. Two thin lenses of power +6D and -2D are in contact. What is the focal length of the combination ?
25. Using the Huygen’s wave theory , verify the law of reflection.

SECTION-C 5X 3=15
Write any 5 of the given questions:

1 1 1
26. Define power of a lens . Write its units. Deduce the relation = + for two thin lenses kept in
f f1 f 2
contact coaxially.
27. The ratio of the widths of two slits in Young’s double slit experiment is 4:1. Evaluate the ratio of
intensities at maxima and minima in the interference pattern.
28. Explain condition for bright fringe and dark fringe in YDSE.
29. (A) Explain the variation of photoelectric current with collector plate potential for different
frequencies and
(B) Variation of photo current with collector plate potential for different intensities at same
frequency.
30. A 4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the
location of the image and the magnification. Describe what happens as the needle is moved farther
from the mirror?
31. Figure (A) and (B) show refraction of an incident ray in air at 60° with the normal to a glass-air and
water-air interface, respectively. Predict the angle of refraction in glass when the angle of incidence
in water is 45° with the normal to a water glass interface [fig.(c)].

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 SECTION-D
Write any 3 of the given questions: 3X 5=15
32. A ray PQ of light is incident on the face AB of a glass prism ABC (as shown in the figure ) and
emerges out of the face AC. Trace the path of the ray. Show that ∠ i +∠ e =∠ A+∠ δ where, δ and e
denote the angle of deviation and angle of emergence respectively.

Plot the graph showing the variation of the angle of deviation as a function of angle of incidence.
State the condition under which ∠ δ is minimum.
33. Derive the mathematical relation between refractive indices µ 1 and µ2 of two radii and radius of
curvature R for refraction at a convex spherical surface. Consider the object to be a point source
lying on the principal axis in rarer medium of refractive index μ1 and a real image formed in the
denser medium of refractive index µ2. Hence, derive lens maker's formula.
34. A plane wavefront propagating in a medium of refractive index ‘µ1’ is incident on a plane surface
making an angle of incidence i as shown in the figure. It enters into a medium of refraction of
refractive index 'µ2' (µ2>μ1).

Use Huygens' construction of secondary wavelets to trace the propagation of the refracted wavefront.
Hence, verify Snell's law of refraction.
35. In a Young's double slit experiment using light of wavelength 600 nm, the slit separation is 0.8 mm
and the screen is kept 1.6 m from the plane of the slits Calculate
(i) the fringe width
(ii) the distance of (a) third minimum and (b) fifth maximum, from the central maximum.

SECTION-E 2x4=8

36. The British physicist Thomas Young explained the interference of light using the principle of
superposition of waves. He observed the interference pattern on the screen, in his experimental set-
up, known now as Young's double slit experiment. The two slits S1 and S2 were illuminated by light
from a slit S. The interference pattern consists of dark and bright bands of light. Such bands are
called fringes. The distance between two consecutive bright and dark fringes is called fringe width.
(i) If the screen is moved closer to the plane of slits S1 and S2, then the fringe width
(a) will decrease, but the intensity of bright fringe remains the same
(b) will increase but the intensity of bright fringe decreases
(c) will decrease, but the intensity of bright fringe increases
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 (d) and the intensity both remain the same
(ii) What will happen to the pattern on the screen, when the two slits S1 and S₂ are replaced by two
independent but identical sources?
(a) The intensity of pattern will increase
(b) The intensity of pattern will decrease
(c) The number of fringes will become double
(d) No pattern will be observed on the screen
(iii) Two sources of light are said to be coherent, when both emit light waves of
(a) same amplitude and have a varying phase difference
(b) same wavelength and a constant phase difference
(c) different wavelengths and same intensity
(d) different wavelengths and a constant phase difference
(iv) The fringe width in a Young's double slit experiment is β. If the whole set-up is immersed in a
liquid of refractive index μ, then the new fringe width will be
β β
(a) β (b) βµ (c) (d) 2
µ µ
37. In 1678, a Dutch scientist, Christian Huygens propounded the wave theory of light. According to
him, wave theory introduced the concepts of wave front. Light travels in the form of waves. A
wavefront is the locus of points (wavelets) having the same phase (a surface of constant phase) of
oscillations. A wavelet is the point of disturbance due to propagation of light. Wave front may also
be defined as the hypothetical surface on which the light waves are in the same phase.
(i) A ray of light wave perpendicular to wavefront
(a) is parallel to a surface at the point of incidence of a wavefront
(b) is the line joining the source of light and an observer
(c) gives the direction of propagation of a wavefront at a given point
(d) is the envelope that is tangential to the secondary wavelets
(ii) A linear source of light produces
(a) cylindrical wavefront
(b) spherical wavefront
(c) plane wavefront
(d) cubical wavefront
(iii) Huygen's principle of secondary wavelets may be used to
(a) find the velocity of light in vacuum
(b) explain the particle behaviour of light
(c) find the new position of the wavefront
(d) explain photoelectric effect
(iv) In case of relection of a wavefront from a reflecting surface,

I. points A and E are in phase difference of 90°.

II. points A and C are in phase difference of 0°.
III. points A and B are in phase difference of 0°.
IV. points C and E are in phase difference of 0°.
Which of the following is correct?

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(a) Both I and II (b) Both II and III
(c) Both III and IV (d) Both I and IV