ch. 17

Question 1

There is a reflection at the boundary between two materials if there is a change of __________ at the boundary.

Answer 1

speed of the light in the materials

Question 2

The colors of a soap bubble or oil slick are due to __________

Answer 2

thin-film interference

Question 3

As the number of slits of a diffraction grating increases, the bright fringes observed on the viewing screen _________

Answer 3

get narrower and brighter

Question 4

In single-slit diffraction, what happens to the dark fringes if the slit gets wider?

Answer 4

they get closer together

Question 5

what is diffraction

Answer 5

it is the spreading of a wave after it passes through an aperture

Question 6

what happens when light waves travel through an object with a higher index of refraction

Answer 6

the speed slows down and the wavelength shortens but the frequency does not change

Question 7

what happens when two light waves overlap

Answer 7

they can interfere constructively or destructively

Question 8

How does the double spilt experiment work

Answer 8

a light beam is shot at two slits, this produces two light sources that can overlap and interfere with eachother which creates patterns on a screen behind them

Question 9

when does constructive interference occur in a double slit experiment

Answer 9

when r1 and r1 pathlengths differ by a whole number of wavelengths, they constrcutively interfere and create brighter bands

Question 10

when does destructive interference occur

Answer 10

when r1 and r2 differ by a whole number of wavelengths and a half they interfere destructively and appear dark

Question 11

what is an interference fringe

Answer 11

it is a series of alternating bright and dark bands of light

Question 12

what is the central maximum

Answer 12

it is where m=0 and it is the brightest fringe

Question 13

in double spilt interference, what is the spacing between the bright lines

Answer 13

it is equally spilt

Question 14

what is diffraction grating

Answer 14

it creates multiple sources of waves that interfere with each other

Question 15

can you use small angle approximation with diffraction grating

Answer 15

no

Question 16

in comparison to the birght fringes in doubke spilt, what is the pattern in the size of the fringes in diffraction grating

Answer 16

they are much narrower

Question 17

in diffraction grating, what happens as the number of slits increases

Answer 17

the fringes get brighter and narrower

Question 18

how is spectroscopy used in diffraction

Answer 18

atomic elements emit certain wavelengths which can affect the angles of lines

Question 19

what is thin film interference

Answer 19

the interference of light waves reflected from two boundaries of a thin film

Question 20

when is light partially reflected from a boundary?

Answer 20

when the two boundaries have different indices of refraction

Question 21

what is a phase change

Answer 21

when a light wave moves from a medium with a lower index of refraction to a higher index of refraction, the reflected wave is inverted and this adds an extra half-wavelength to the distance the wave travels

Question 22

when does light undergo a phase change

Answer 22

if it reflects from a boundary where the index of refraction increases

Question 23

when will two reflective waves interfere constructively

Answer 23

when their crests are in phase and it causes a strong reflection

Question 24

when will two reflected waves interfere destructively

Answer 24

when their crests are out of phase and they reflect weakly

Question 25

if n1<n2, is there a phase shift in thin film

Answer 25

yes

Question 26

if there is 1 phase shift, what happens to the formula 2t=m (wavelength)/n

Answer 26

the conditions for a constructive wave becoem destructive

Question 27

if there is 0 or two times that n1<n2, what happens to the formula 2t=m (wavelength)/n

Answer 27

it means the conditions for constructive remain constructive

Question 28

what is single slit diffraction characterized by

Answer 28

the light pattern has a central maximum and a series of weaker secondary maxima and dark fringes

the central maximum is much brighter than the secondary

Question 29

what is huygen’s principle

Answer 29

each point on a wave front is the source of a spherical wavelet that spreads out at the wave speed

at a later time, the shape of the wave front is the curve that is tangent to all the wavelets

Question 30

why is there a central maxima

Answer 30

the paths of several wavelets travel straight ahead and are in phase so they add constructively at theta= 0

Question 31

every point on the wave front can be paired with another that is

Answer 31

a/2 distance away

Question 32

for single-slit diffraction, the smaller the openig a wave squeezes through, the _______ it spreads out onto the other side

Answer 32

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