Light Guided Notes
Name:________________________
EM Spectrum
What we call “light” is merely a small fraction of the total _____________________________________.
The electromagnetic spectrum
Consists of ___________________________ of varying frequencies
Occur due to oscillation of electric and magnetic fields
______________________________________________________________________
Travel at the speed of light (c = 3.00 X 108 m/s) in a vacuum
Vision
We see when light when visible light enters our eyes and focuses on our retinas.
The light may come from a _______________________ source (something that emits light, such as the sun or
a light bulb) or may bounce (reflect) off an ___________________________ object.
We have photoreceptor cells in our retinas that send a signal to our brain whenever light hits them.
• ___________ are sensitive to all wavelengths of visible light
 provide black and white vision
• ____________ are sensitive to only certain wavelengths
 provide color vision
We have three cones types:
___________, _____________, ___________
Our brain interprets color based on the combinations
of cones that are triggered by certain light.
… if only the red cone is triggered, we see
… if red and green are triggered equally, we see
Different materials absorb, reflect, and/or transmit different wavelengths of light.
• __________________________ – light energy that has the same natural frequency as the
electrons in the object will be absorbed – the energy will be converted into vibrational motion
of the electrons.
• _________________________ – the light ‘bounces off’ the surface of the object
• __________________________ – the light goes through the object and out the opposite side
Which type of light hits our eyes? _________________________
_________________________________ objects transmit most of the light that hits them.
_________________________________objects transmit some of the light that hits them.
_________________________________ objects reflect or absorb most of the light that hits them.
How would the following objects appear?
1. An object that reflects blue and green light; absorbing other wavelengths.
2. An object that reflects all visible light waves.
3. An object that absorbs all visible light waves.
4. An object that reflects pink light but transmits all other wavelengths.
5. An object that transmits most of the light hitting it.
Barrier Behavior of Waves
Waves of any sort – light, sound, water, etc. – exhibit different behaviors when they encounter a barrier.
• ________________________ – bouncing back of a wave as it encounters a new medium
• ________________________ – the bending of a wave as it transmits through a different medium
• ________________________ – The separation of a wave into its component frequencies
• ________________________ – the spreading of a wave behind an obstruction
Light – faster in air than water
Sound – faster in water than air
Frequency is determined by the source so it doesn’t change. Only wavelength changes. Wavelength of the
same wave is smaller in the medium with smaller speed.
Snell’s Law
We can predict the degree of refraction using Snell’s Law
Snell’s Law states that the ratio
is constant for the given frequency.
The Snell’s law is of course valid
for all types of waves.
Greater speed – _________________________
Slower speed – __________________________