Question

Concerning electromagnetic rays:

a. They travel parallel to each other in a straight line

b. Beam intensity is proportional to the square of the amplitude

c. The area of the beam is proportional to the square of the distance as it travels away from a point source

d. Beam intensity is proportional to the square of the distance as it travels away from a point source

e. The inverse square law is useful for estimating the intensity of a beam once it has passed through a copper filter

Answer 1

a. False. Electromagnetic rays originate from a point source and diverge out, travelling in a straight line, unless attenuated.

b. True.

c. True. The inverse square law states that the intensity of radiation emitted from a point source will reduce in intensity, proportional to the square of the distance from that point, i.e. the area covered by the beam increases as the rays are diverging from a point; however, the number of photons *** the same and hence their intensity reduces.

d. False.

e. False. Important points to remember regarding the inverse square law are:

i. Radiation comes from a point source.

ii. There is no absorption or scatter of radiation between source and point of measurement.