Module 4 - Waves (Intensity and Amplitude)

Question 1

What is meant by intensity

Answer 1

The radiant power passing at right angles through a surface area per unit area

Question 2

What is the unit of intensity and what is it equal to

Answer 2

(Wm^-2) = One joule being transferred to one square metre area in one second

Question 3

What happens to Light, Sound and EM waves as they travel

Answer 3

• Light gets dimmer
• Sound gets quieter
• EM waves have lower intesity

Question 4

What is teh equation for intensity

Answer 4

I = P/A

Question 5

True or false a wave radiates in all directions at the same speed in the same medium

Answer 5

True

Question 6

If there is a point source of light, after one second:

a) how far has it travelled

b) in what directions does all the enrgy transfer

c) what is the surface area through which the radiant power passes through

Answer 6

a) 300,000,000 m
b) in all directions
c) 4πr², where r is 300,000,000m

Question 7

What is the intensity equation for a point source

Answer 7

I = P/4πr², where r is the distance travelled by the wave

Question 8

What is the relationship between the intensity and the distance from the source given a constant power

Answer 8

I α 1/r²

Question 9

What is the relationship between intensity and amplitude, and describe with an example

Answer 9

• I α A². If the amplitude increased by a factor of x, then the intensity increasees by a factor of x²