Waves

Question 1

Transverse wave

Answer 1

oscilations are perpindicular to the direction of travel, (travel in vaccum) e.g. light

Question 2

Longitudinal

Answer 2

oscilations are paralell to direction of energy travel e.g. sound

Question 3

Wave definition

Answer 3

transfer of energy without transfer of matter

Question 4

formula for frequency of a wave on a string

Answer 4

n/(2L) X √(T/μ)

Question 5

superposition

Answer 5

addition of displlacement of waves (destructive/constructive interference)

Question 6

speed of a wave on a string

Answer 6

V=√(T/μ)

Question 7

N/(2L) =

Answer 7

1/λ

Question 8

how is a standing wave produced(on guiter)

Answer 8

• two waves travel in opposite position
• waves are coherent
• superpose/interfere
• constructive if in phase
• destructive if in antiphase
• nodes formed during constructive interference where max displacement
• antinodes formed in destructive interference where min displacement

Question 9

how does sound travel through air

Answer 9

longitudinal wave in air with osilations paralell to the direction of energy transfer

Question 10

what is a photon

Answer 10

a descrete packet of energy

Question 11

momentum of photon

Answer 11

p = h/wavelength

Question 12

energy of photon

Answer 12

e = hf / hc/wavelength

Question 13

how does photoelectric effect work to emit an electron

Answer 13

• Photon hits surface of metal
• e=hf
• Metal has required energy to emit an electron from surface known as work function
• Certain frequency is needed to overcome work function (WF)
• Photons energy transfered to electron on surface
• 1 to 1 occurence, either absorbs all or doesnt any
• Excites electron to be emitted
• Hf = WF + Ek(max)
• Some require more WF to move electron to surface hence lower Ek

Question 14

how does emmision spectra work in a discharge tube

Answer 14

• high p.d will accelerate electron toward posative terminal
• electron collides with atom when moving
• excites atom as energy is transfered to atom
• causes an electron (in atom) to move up energy level
• electron falls back down energy level
• this emits a photon causing spectra
• the number of oppertunities for the electron to fall creates the number of line spectra seen
• some spectra are not on light spectrum so wont be seen

Question 15

Huygens construction principle

Answer 15

wave diffracts because each point on wavefront acts as a seondary wave emited from original wavefront

Question 16

why bright light at center after difraction

Answer 16

path diffrence at spot is 0/equal. thus will be in phase thus bright spot of constructive interference

Question 17

why is a model accepted

Answer 17

reproducable
could be repeated by others
agrees with other theories and evidence

Question 18

monochromatic

Answer 18

single frequency

Question 19

coherent

Answer 19

single frequency and constant phase relationship

Question 20

virtual image

Answer 20

cant be formed on screen, image formed from apparent divergence of light from single point