Astro lesson 3

Light acts as an Electromagnetic wave

A varying Electric field causes a varying Magnetic field which causes a varying Electric field.

This allows a light wave to be self sustaining and travel without a medium (They transmit in a vaccum)

light refracts and slows down when it changes medium (it moves the fastest in a vacuum and slows down in mediums like water and glass

Light changes speed when it enters a medium. Changing speed causes a bend in the lights path as it

changes medium. This change in speed is dependent on the wavelength (color).

characteristics of waves

(energy and frequency are proportional)

• wavelength

• speed

• amplitude

• hertz

• frequency

• v=(wavelength)*f

Electromagnetic wave equation

gamma rays

They have the highest frequencies of all (highest energy), above 1020 Hz. These rays are extremely

energetic, and are produced in nuclear reactions. They are destructive to living cells and are

therefore used to destroy cancer cells and to sterilize food.

X-rays

They have high frequencies, from 1017 Hz to 1020 Hz. They are used for medical imaging.

The wavelengths are powerful enough to penetrate flesh but will interact with denser

bones.

UV Light

Ultraviolet light starts with frequencies just above those of visible light, from 7.5 x 1014

Hz to 1017 Hz. These rays cause tanning, burning, and skin cancer. Some insects can see in

the ultraviolet, and some flowers have special markings that are only visible under

ultraviolet light.

E=hf calculation

h=plancks constant = 6.63x10-34 Js

(Most Important Slide from this lesson)