p5.1 - grey bits (yr11)

Question 1

when does reflection occur?

Answer 1

when a wave hits a hard, smooth surface

Question 2

what is refraction?

Answer 2

the change in direction of waves as they travel across a boundary between two different media

Question 3

what is a medium?

Answer 3

any space which is full of matter of the same density

Question 4

what 3 features change in waves when they cross a boundary between two different media?

Answer 4

• speed changes
• direction changes
• they slightly bend

Question 5

describe the behavior of EM waves when they travel from a high-density medium to a low-density medium

Answer 5

velocity - increases
frequency - remains same
wavelength - increases (same as velocity)

normal - bends away from normal (more velocity)

Question 6

what is one way to remember how the wavelength changes during refraction?

Answer 6

• must balance (v = w x f) out

as frequency always remains constant

Question 7

describe the behavior of EM waves when they travel from a low-density medium to a high-density medium

Answer 7

velocity - decreases
frequency - remains same
wavelength - decreases

normal - bends towards normal (slows down)

Question 8

how does the velocity/wavelength/frequency change during reflection?
(and why)

Answer 8

all remain the same
- as it carries on travelling through the same medium (travel through air, reflected off mirror, carry on through air)

• and the medium determines the speed + wavelength of a wave through it

Question 9

what is the reason you can see an object?

Answer 9

the object is emitting/reflecting light

Question 10

how do you draw the normal line?

Answer 10

it is perpendicular (90 degrees) to the boundary

Question 11

what does the law of reflection show?

Answer 11

the angle of incidence is equal to the angle of reflection

Question 12

what 3 things can happen to a sound wave at a boundary?

Answer 12

• reflected
• refracted/transmitted
• absorbed

Question 13

what factor affects what happens to a sound wave at a boundary?

Answer 13

the density of the regions either side of the boundary

Question 14

what is ultrasound and why is it useful?

Answer 14

• wavelength with high frequency ( > 20 000 Hz)
• useful as it has a small wavelength
• and can be focused into a beam

Question 15

why does the colour remain same during refraction?

Answer 15

as the frequency remains same (and colour is dependant on frequency)

Question 16

in terms of electrons, what happens when a wave is reflected?

Answer 16

electrons absorb light energy, then reemit it as a reflected wave

Question 17

what does it mean if light is transmitted?

Answer 17

it passes through the material + emerges

Question 18

when does absorption happen? (electrons absorbing light)

Answer 18

when the energy of light absorbed matches the difference in energy levels of the electrons

Question 19

what does it mean if a material appears a certain colour?

Answer 19

only that coloured light has been reflected, all other frequencies of light have been absorbed