1. If light travels a million times as fast as sound, why does the sound from yo

Question

1. If light travels a million times as fast as sound, why does the sound from your television set appear to be "synchronized" with the picture you see?

2. The distance light travels in one year is called a light year. How many kilometres are there in one light year? What is the distance of the sun from the earth in light years?

3. What is the wave length of a 32 MHz cell phone signal? (recall that: 1mhz = 1*10^6 s^-1).

4. If the "hot spots" of a plate of marshmallows cooked in a microwave oven for 5 min. are 5.3 cm apart, what is the frequency of the microwaves?

Explanation / Answer

1. since the distance is too short, when compared to the values of speeds of sound and light , the delay cannot be detected

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2. 1 light year 1LY = 9.46 *10^15 m

as 1km = 1000m

so

1 LY = 9.46*10^12 km

Distance from sun to earth = 1.5*10^11 m

in terms of lightyears Distance = 1.5 *10^11/9.46*10^15 = 1.5*10^-5 Ly

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3. velocity V = Wavelength L * frequency f

so

L = (3*10^8)/(32*10^6)

L = 9.375 meters

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4. frequency f = 1/t

f = (1/(5.3*60)

f = 0.0031 Hz

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