Question

I need help with all 4

1) 1) A plane wave is projected towards a small opening in a wall and spreads out once it passes the opening. Rank in order the amount of diffraction of each wave below from most spreading to least spreading. A) Most>Ocean wave, Sound wave, Blue light, Red light+Least. B) Most Red light, Blue Light, Ocean wave, Sound wave Least. C) Most →Blue light, Red Light, Sound Wave, Ocean wavefLeast. D) Most Sound wave, Ocean wave, Red Light, Blue Light Least. E) Most+Ocean wave, Sound wave, Red Light, Blue LightLeast. 2) 2) A siren creates a sound of 100 decibels at a distance of 10 m. At 100 m, the sound intensity level is A) 90 dB B) 100 dB C) 10 dB D) 80 dB E) 1.0 dB 3) 3) Which of the following is a false statement? A) A yellow star approaching the earth will appear orange (i.e. more red). B) If you bike towards a stationary fire alarm it will sound higher pitched than if you were stationary. C) If you are driving ahead of a moving train at the same speed as the train it will sound the same as if neither you nor the train were moving. D) Distant galaxies appear red-shifted because of the expansion of the universe. E) A cop hiding behind bushes watches you speed past him with a radar gun. As you are driving away from him, the radio waves reflected from your car return to the gun with a lower frequency than the emitted waves. 4) 4) A slide has a rectangular opening with both a width w and a length 1, where w, 1-2. When a laser is shined at the opening the interference pattern shown at right is observed on a screen behind the slide. Which of these diagrams most accurately represents the rectangular opening? A) B) C) D) E)

Answer 1

6) ß = 10 log (11) 100 = 18 log log ( 7 ) 10 10 X 10-12 = I, -) I = 0.01 Why? using I, d, ² = J, de ² = 0.01x (or = I, (100)* -) Iz = 0.00ol wlm? ::B=colog (6) ) 10 o log ( 10 ) - 10 log (109) - 180 dB (3) Doppeler's formula, fobserved - foriginal (Vound + Vebserver Vsound - Vsource ..If speed ofdren and you are some, then fobserved & foriginal -; (c) option is false.