Electromagnetic Spectrum and Light

Electromagnetic Waves

vibrating charged particles oscillating electric and magnetic field, all transverse waves, no medium required

Speed in a vacuum

c = 3 × 10^8

relationship between λ and f

inversely related ex) f = v/λ, wavelength is largest on lower end of spectrum and frequency is smallest and vice versa

Electromagnetic Spectrum Order

Radio, Microwave, Infrared, Visible, Ultraviolet, X-Ray, Gamma Ray

Colors of visible light spectrum

red, green, and blue- they mix to make cyan, magenta, and yellow

White Light

created through addition of all primary colors of light

How color shows

the hue not seen is absorbed ex) cyan absorbs red and reflect green and blue light

What things can light do when it hits something?

reflect, absorb, or transmit

Law of Reflection

angle of reflected ray equals the angle of the incident ray

How are the angles measured?

relative to the normal (draw in perpendicular line)

Specular Reflection

related to light reflecting off a smooth surface

Diffuse reflection

related to light reflecting off a rough surface

Plane Mirrors

flat and everything reflects accurately

Spherical mirrors

Concave (magnify) where its shaped like the inside of a sphere and convex (wider) where its shaped like the outside of a sphere

Refraction

Changing of speed as a wave crosses a boundary into a different medium- causes a change in direction and thus associated ray

Index of Refraction (n)

Material property that determines how much light slows/speeds up across a boundary — n = c/v where n=1 is the index for air. NO UNITS!!

What property of light waves change when the speed does?

λ changes but f remains constant

relationship between speed and index of refraction

as n increases, v decreases and vice versa

n1 < n2

wave slows down and ray bends toward normal, θ1 > θ2

n1 > n2

wave speed up and bends away from normal, θ1 < θ2

Snells Law

n1sin1 = n2sin2

Dispersion

with non-parallel boundaries, the different index of refractions in different lights will cause them to bend different amounts— white light spreads out

Total Internal Refraction

when you speed up across a boundary, sometimes the refracted ray would be greater than 90 degrees as it bends away from the normal. At θin > θc, all light is reflected

Critical point θc

refracted ray travels along the boundary. θc = θin for θr = 90