Waves and optics(1)

1. Waves and OpticsWaves and Optics
Nisha Issac (: & Ethan MunguiaNisha Issac (: & Ethan Munguia

2. InterferenceInterference
When two waves pass through the same When two waves pass through the same
region of space at the same timeregion of space at the same time
2 types: 2 types:
Constructive: crest to crest; larger amplitudeConstructive: crest to crest; larger amplitude
Destructive: crest to trough; resultant is zero if Destructive: crest to trough; resultant is zero if
both the waves have same amplitude.both the waves have same amplitude.

3. DiffractionDiffraction
Refers to the ability of waves to bend Refers to the ability of waves to bend
around obstacles around obstacles
Amount of diffraction depends on the Amount of diffraction depends on the
wavelength of the waves and the size of wavelength of the waves and the size of
the obstacle. the obstacle.
In the case of narrow opening, the amount In the case of narrow opening, the amount
of bending increases as the size of the of bending increases as the size of the
opening decreases.opening decreases.

4. Dispersion of lightDispersion of light
Spreading of white lightSpreading of white light
Dispersion of light in a transparent Dispersion of light in a transparent
material occurs because the index of material occurs because the index of
refraction of the material varies the refraction of the material varies the
wavelength.wavelength.
Index of refraction is higher for shorter Index of refraction is higher for shorter
wavelengthswavelengths

5. Electromagnetic SpectrumElectromagnetic Spectrum
Radio waves, Microwaves, Infrared, Radio waves, Microwaves, Infrared,
Ultraviolet, X-Rays, Gamma RaysUltraviolet, X-Rays, Gamma Rays

6. ReflectionReflection
““Bouncing” off of a wave of a surface; Bouncing” off of a wave of a surface;
exact angleexact angle
Angle of incidence = Angle of reflectionAngle of incidence = Angle of reflection
The angle of incidence is the angle that The angle of incidence is the angle that
light is striking a surface. The angle of light is striking a surface. The angle of
reflection is the angle that the light is reflection is the angle that the light is
reflected, or bouncedreflected, or bounced

8. RefractionRefraction
Change in direction of a wave when it passes Change in direction of a wave when it passes
into a new substanceinto a new substance
Reason it changes direction or bends is because Reason it changes direction or bends is because
each different substance has its own effect on each different substance has its own effect on
speed of light.speed of light.
Index of refraction- Equals the ratio of speed of Index of refraction- Equals the ratio of speed of
light in a vacuum to the speed of light in a light in a vacuum to the speed of light in a
transparent substance. Determines the angle of transparent substance. Determines the angle of
bending of the light at the interface between two bending of the light at the interface between two
transparent substances. transparent substances.

9. MirrorsMirrors
Reflective surfacesReflective surfaces
Convex and Concave Convex and Concave
Has a focal point, where all the light Has a focal point, where all the light
directed at that mirror converges or directed at that mirror converges or
diverges and the distance between the diverges and the distance between the
mirror and that point is the focal length. mirror and that point is the focal length.

10. LensesLenses
Has a focal point Has a focal point
Focal point of the lens- point where rays Focal point of the lens- point where rays
parallel and very close to the principal axis parallel and very close to the principal axis
all pass through after refraction by the all pass through after refraction by the
lens.lens.
Focal Length- distance from the center of Focal Length- distance from the center of
lens to focal pointlens to focal point
Radius of curvature of a lens is exactly Radius of curvature of a lens is exactly
twice the focal length. twice the focal length.

11. Important FormulasImportant Formulas
θθ = the angle of spread of a wave after passing = the angle of spread of a wave after passing
through a single slit openingthrough a single slit opening
λ λ = wavelength= wavelength
fn fn = the = the nthnth frequency in a series of resonant frequency in a series of resonant
frequenciesfrequencies
v v = speed of the wave= speed of the wave
LL = length = length
DD = width of an opening through which a wave = width of an opening through which a wave
will diffractwill diffract
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12. Example #1
A ray of light strikes the surface of a flat glass
plate at an incident angle of 30(degree). The
index of refraction of air and glass are 1.00 and
1.50, respectively. Determine the a) angle of
reflection and b) angle of refraction.
Answer:
The reflected ray follows the laws of specular
reflection and so the angle of reflection is 30 degrees
Snell’s law; 19 degrees

13. Example #2
A laser beam is incident on 2 slits separated
by .500mm. The interference pattern is formed
on a screen 1.00m from the slits & the 1
st
fringe
is found to be .120cm to the right of the central
maximum. A) Calculate the wavelength of the
light in nm & b) determine the maximum number
of bright fringes that can be observed.
Answers:
A: 6.00 x 10
-7
B: m=833

14. Example #3
A radar pulse travels from Earth to the
moon & back in 2.60 secs. Calculate the
distance from the Earth to the moon in a)
meters and b) in miles
Answers:
d= 3.90 x 10
8
m
d= 2.42 x 10
5
miles