Q # 1
Measuring wavelengths with a CD, A LASER beam of wavelength λ = 632.8nm shines at
normal incidence on the reflective side of a compact disc. The track of tiny pits in which information is coded onto the CD are 1.60µm apart. For what angles of reflection
(measured fro m normal) will the intensity of light be maximum? Marks = 7



Q # 2
The plate on the back of a certain computer scanner says that the unit draws 0.34A of current from a 120V, 60Hz line. Find (a) the root mean square current (b) the current amplitude (c) the average current (d) the average square current. Marks = 8

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Q # 3
Give several examples of electromagnetic waves that are encountered in everyday life.
How are they all alike? How do they differ? Marks = 5

--Gamma rays are emitted by thallium nuclei during stress tests for heart disease.
--X-rays are used to image body interior parts either in "photos" or CT scans.
--Ultraviolet light from the sun or tanning lamps has cosmetic effects.
--Visible light illuminates dark nights or rooms. It also exposes films for photography.
--Infrared light is used by some stoves for cooking. Infrared lamps keep hot food warm.
--Microwave radiation also cooks food or boils water.
--Radar waves are used by airplane pilots, ground observers, and ship and boat crews to image solid objects in fog or darkness.
--Radiofrequency radiation interacts with strong magnetic fields to view interior body
parts by magnetic resonance imaging. Lower energy radio waves propogate radio and TV
signals