Transverse Wave

Electromagnetic Spectrum

Electromagnetic Waves

• Do not require a medium to travel, unlike mechanical waves

• Exhibits interactions that are true for all waves: Reflection (scatter), Refraction, Diffraction, and Interference

• Speed of light ~300,000,000 m/s in a vacuum (sound in solids = 5,200 m/s)

What happens to light when it enters matter?

3. Transmitted – passing of EM waves through a medium (includes refraction) *transparent –light passes through *translucent – light passes through but is scattered *opaque-light does not pass through but reflects or absorbs

2. Absorbed – the disappearance of an EM wave into the medium. This light is converted to heat.

1. Reflected – includes scattering which is the spreading out of light rays in all directions

Two factors determine the color of an object:

1.The wavelengths that the object itself reflects or absorbs

2.The color of the light that shines on the object

Green and Blue Light is Absorbed By the Apple

What color band does a white flower absorb?

Law of Reflection

Law of Reflection

a. regular reflectionb. diffuse reflection

*A prism refracts (bends) light*Shorter wavelengths bend more

Refraction of light towards the normal in a more dense medium (air to water)

Refraction: Waves change speed and bends when entering a new medium

Diffraction spike - Diffraction spikes are lines radiating from bright light sources in reflecting telescope images. They are artifacts caused by light diffracting around the support vanes of the secondary mirror. Refracting telescopes and their photographic images do not have the

same problem

Absorbs and reflects

Anatomy of the Eye

The Eye

Color Blindness Test Cow Eye Dissection• http://www.exploratorium.

edu/learning_studio/cow_eye/

http://colorvisiontesting.com/online%20test.htm#Test%20Card%20Number%202%20answer

Refraction

NearsightednessFarsightedness

http://www3.nd.edu/~ysun/Yang/PhysicsAnimation/html/list.html

Concave & convex mirrors

 (M.C. Eshcher) 

Images in a convex mirror are always smaller than the object.

Concave Mirror

SOMETHING THAT PRODUCES ITS OWN LIGHT IS SAID TO BE

LUMINESCENT

Produces light by heating up, so it much of the energy ends up as heat. Only 10% of the energy is converted to visible light. The rest is converted to infrared.

Fluorescent light – filled with a mercury vapor and other gases that give off UV light when an electric current passes through it.

Chromatophores are pigment-containing and light-reflecting cells found in amphibians, fish, reptiles, crustaceans, and cephalopods.

What is the name for the production of light from high temperatures or intense heat?

INCANDESCENCE

What is the name for the production of light from chemical reactions?

BIOLUMINESCENCE

What is the production of light when a material absorbs EM radiation ofone wavelength and give off EM radiation of a different wavelength?

FLUORESCENCE

RED SHIFT (Doppler Effect)• It is the fact that sound

travels in waves that allows the

Doppler effect to happen. • Electromagnetic radiation,

which includes visible light, also travels in

waves, so the Doppler effect happens

with light too: as an object travels

towards you at speed, the light waves being

emitted (or reflected) by it are squished color.

Red ShiftThis spectral linewill move towards the red end ofthe spectrum whenlight from a staris moving away