A. Radio waves have a wavelength of 50 m in air (or vacuum), and a speed of 2.1x

Question

A. Radio waves have a wavelength of 50 m in air (or vacuum), and a speed of 2.1x108 m/s in saltwater. What is the wavelength of these waves in saltwater?

a) 21 m

b) 35 m

c) 50 m

d) 74 m

B. In which of the following cases would you expect to observe strong diffraction?

a) 6.0 cm water waves incident upon a 5.0 cm slit

b) 10 nm UV light incident upon a 5.0 cm slit

c) 3.0 m radio waves incident upon a 900 nm slit

d) 2.0 m water waves incident upon a 5.0 nm slit

C. Two +4.0 nC charges are 30 cm away from a point P. What is the magnitude of the electric field at point P?

a) 800 N/C

b) 570 N/C

c) 380 N/C

d) 0 N/C

D. Draw the ray diagram of the lens and mirror system below (3 special rays).

E. A beam of white light is incident on a thick piece of N-BK7 at a 60° angle to the normal, as shown below. Which of the following statements are true about the light as it moves through the N-BK7 glass?

a) The light spreads with red on top, violet on bottom

b) the light spreads with violet on top, red on bottom

c) the light spreads randomly organizing colors

d) the light remains a beam of white light and doesn't spread

Explanation / Answer

a) When the light going from one medium to another medium its velocity gets changes according to the refractive index but the wavelength remains constant.

Ans: 50 m: (c)

b) Condition for the diffraction is that slit width must be comparable to that of wavelength which is well matching for the diffraction of 6cm water through a slit of width 5 cm.

ans : (a)

e) the deviation in the light beam is inversely proportional to the wavelength. So the violet will be at bottom and red will be at top.

Ans: (a)

(c) For this we need the value of theta or the distance between the two charges.

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