BPHCT-137 · December 2023 · English
IGNOU BPHCT-137 December 2023 Previous Year Question Paper
WAVES AND OPTICS
Structured previous year question paper for BPHCT-137, December 2023 session.
Max marks: 50 · Questions: 6
Verified: 24 Aug 2026
BACHELOR OF SCIENCE (GENERAL)
(BSCG)
Term-End Examination
December, 2023
BPHCT-137 : WAVES AND OPTICS
Time : 2 Hours Maximum Marks : 50
Note :
(i) All questions are compulsory. However,
internal choices are given.
(ii) You may use a calculator.
(iii) Symbols have their usual meanings.
(iv) The marks for each question are
indicated against it.
Q1.Attempt any five parts : 5×2=10
(a) Draw the labelled diagram of three level pumping scheme for a laser.
(b) What do you understand by critical angle of an optical fibre ? Give its expression in [ 2 ] BPHCT–137 terms of refractive indices of core and cladding of the fibre.
(c) Sound is a wave phenomenon. How is it different from light waves ?
(d) Define resonance and give one example.
(e) What is dichroism ? Name a simple dichroic device.
(f) State differences between b iprism and Lloyd’s mirror fringes.
(g) Write conditions for obtaining bright and dark fringes by a wedge-shaped film.
(h) Depict spatial evolution of Fresnel diffraction pattern.
Q2.Answer any two parts : 2×5=10
(a) Calculate the speed of sound in sea water and steel. Explain your result. Given : sea water 31023kgm , B = 2.34 ×109 Nm–2 Y = 20 × 1010 Nm–2 and steel 7800 kg 3m . [ 3 ] BPHCT–137
(b) Obtain expression for apparent frequency when the source of sound is in motion towards the listener who is stationary.
(c) What is birefringence ? Discuss how Nic ol prism can be used to obtain plane polarized light.
Q3.Answer any two parts : 2×5=10
(a) What do you understand by interference of light by division of wavefront ? Discuss Young’s double slit experiment to obs erve interference.
(b) In interference experiment, obtain expression for displacement of fringes when a thi n transparent sheet is introduced in the path of one of the beams.
(c) Show that the condition for destructive interference of light reflected by a thi n film is : 2 cost r n [ 4 ]
Q4.Answer any two parts : 2×5=10
(a) Describe any two activities to observe diffraction of light outside the laboratory condition.
(b) Obtain expression for intensity of diffraction pattern produce d by a single slit.
(c) Light from a laser in incident on a grating having 5300 lines per cm. The central and first order principal maxima are s eparated by a distance of 0.48 m on a screen placed
Q5.5 m away from the grating . Calculate the wavelength of laser light.
Q6.Answer any two parts : 2×5=10
(a) Discuss any five advantages of using optical fibre for communication.
(b) Explain the working of Nd : YAG laser with the help of appropriate labelled energy level diagram.
(c) Light of wavelength 5800 Å has a spread of