Question

How do the following types of radiation interact with matter?

a) radio waves

b) microwaves

c) infared

d) visible light

e) ultraviolet, x-rays and gamma rays

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a) How do wavelength and frequency change as you move through the EMR spectrum?

b) What is special about the visible range of the EMR spectrum?

(Please type your responses and be succinct.)

Answer 1

(a) Interaction of radio waves with matter :

When radio waves intersect matter, an induced oscillating electric field is developed having frequency equal to the frequency of waves.

If the matter is metallic then the free electrons of metals will move back and forth due to the influence of electric field. Thus, a small induced electric current is produced. It can be detected and amplified and used to convey information about the radio waves. The antenna works on the same phenomenon.

(b) Interaction of micro waves with matter :

When microwaves interact with matter, the molecules of the matter rotate and heat is generated. The conductors will absorb microwaves and gets heated.

In microwave ovens, the microwave passed through the food items more rapidly and producing molecular rotations and torsions.

(c) Interaction of infrared radiations with matter :

The infrared radiations absorbed more strongly than microwaves, thus the matter is heated due to the increased molecular vibrational activity. The infrared radiation penetrates the skin and thus they are used for the photographic imaging of the blood vessels.

(d) Interaction of visible radiations with matter :

The visible light absorbed by the matter and then the electrons move to the higher energy levels.

(e) Interaction of ultraviolet, gamma and X rays with matter :

The ultraviolet radiations are strongly absorbed by the skin and thus the dangerous photoionization take place. It may lead sun burn and skin cancer.

The ozone layer absorbs most of the ultraviolet radiations from the sun before it reaches the surface of earth.

The X rays interacts with the electrons only by knocking it completely out of the atom. This leads the Compton effect.

At high energy levels, the X ray photons can create electron positron pair.

(a)

Increasing order of the wavelength of EMR

Gamma < X rays < UV rays < Visible < Infrared < Micro < Radio

Decreasing order of frequency of EMR

Gamma > X rays > UV rays > Visible > Infrared > Micro > Radio

(b) The visible range can be detected by the humans as this frequency is detected by the humans .