LIGHT WAVES
• Light is an electromagnetic wave.
• Its motion is transverse.
• Light travels in straight lines.
Visible light- the set of light wavelengths that stimulate the retina of the eye.
ROY-G-BIV
VISIBLE LIGHT RANGE:
Wavelength: 400nm – 700nm
(1nm= 1x10-9m)
4x10-7m – 7x10-7m
SPEED OF LIGHT:
c = 3 X 108m/s
This is the same for all electromagnetic waves!!!!
AS WAVE LENGTH INCREASES, FREQUENCY DECREASES.
f (Hz)
λ (m)
V = fλ where v is always the speed of light.
ELECTROMAGNETIC SPECTRUM
Infrared rays- frequency is lower than visible light. Responsible for heating the earths atmosphere.(less then 4.3x1014Hz)
Ultraviolet rays- frequency higher than visible light. Responsible for skin cancer. (greater than 7x1014Hz)
Low frequency High frequency
Infrared ROY-G-BIV ultraviolet
High λ Low λ
Low energy high energy
velocity is always 3x108m/s velocity is always 3x108m/s velocity is always 3x108m/s
TERMSLuminous- a body that emits its own light.
Illuminated- Body that reflects light.
Transparent- a medium that allows light to travel through it.
Translucent- distorts light.
Opaque- reflects or absorbs light.
PHOTOMETRY The study and measurement of visible light in terms of its perceived brightness to human vision.
SOURCES OF LIGHTIncandescent light-
object gives off light when heated.
• Neon Light – Light produced when electrons in a tube of gas are excited.
Fluorescent light- Ultraviolet rays strike a white powder coating on the inside of the bulb causing it to glow.
• Black light- High frequency visible light (purple) which can cause other objects to fluoresce or glow.
LED- light emitting diode
• Laser light- Light amplification by stimulated emission of radiation
Laser light is monochromatic (one color) and coherent (in phase). This produces a
small beam instead of scattered light
https://www.youtube.com/watch?v=UG85VgLOdPA