Physics (9.3.23)

Question 1

What are waves?

Answer 1

Waves tranfer energy and information without transferring matter (particles oscillate about a fixed point)

Question 2

What is a Transverse wave?

Answer 2

-Have peaks and troughs
-Oscillations (vibrations) are perpendicular to the direction of energy (wave)
-Eg: light

Question 3

What are Longitudinal waves?

Answer 3

-Consists of compressions and rarefractions
-Oscillations (vibrations) are parallel to the direction of energy (wave)
-Eg: sound

Question 4

What is the Amplitude of a wave?

Answer 4

the distance from the equilibrium position to the maximum displacement

Question 5

What is the Wavefront of a wave?

Answer 5

the front of a wave, or the same point on each wave

Question 6

What is the Frequency and its units?

Answer 6

-The number of waves passing through a point per second
-Hz (hertz)

Question 7

What is the Wavelength?

Answer 7

The distance between two adjacent peaks on a wave

Question 8

What is meant by the period of the wave?

Answer 8

The length of time it takes for one full wave to pass through a point

Question 9

How can you calculate the wave speed?

Answer 9

speed = frequency x wavelength
v = f x λ

Question 10

State an equation linking frequency and period of a wave

Answer 10

Frequency (Hz) = 1/ period (s)
f = 1/T

Question 11

What are Mechanical waves?

Answer 11

-waves that need to pass through a material
-made from vibrations of that material
-eg: sounds waves, seismic waves, strings

Question 12

What are Electromagentic waves?

Answer 12

-Transverse
-Travel at the speed of light in vacuum
-Can be reflected, refracted or diffracted
speed = 3x10 (to the power of 8) m/s

Question 13

What is the order of the Electromagnetic spectrum?

Answer 13

Radio wave, Microwave, Infrared radiation, Visible light, Ultraviolet, X-Ray, Gamma Ray

Question 14

Uses of Radio waves and Microwaves

Answer 14

-broadcasting and communications
-cooking and satellite transmissions

Question 15

Uses of Infrared, Visible light, and Ultraviolet

Answer 15

-heaters and night vision equipment
-optical fibres and photography
-fluorescent lamps

Question 16

Uses of X-Rays and Gamma rays

Answer 16

-observing the internal structures of object and materials, including for medical applications
-sterilising food and medical equipment

Question 17

Detrimental effects of microwaves and simple protections

Answer 17

internal heating of body tissue - using an oven

Question 18

Detrimental effects of Infrared and Ultraviolet and simple protections

Answer 18

-skin burns - protective clothing
-damage to surface cells and blindness - sunscreen

Question 19

Detrimental effects of Gamma Rays and simple protections

Answer 19

cancer, mutation - led, concrete

Question 20

What does the Law of Reflection state?

Answer 20

Angle of incidence = angle of reflection

Question 21

State an equation linking angle of incidence, angle of refraction and refractive index (law of refraction)

Answer 21

refractive index = sin (angle of incidence)/ sin (angle of refraction)
n = sin(i)/sin(r)

Question 22

What is the total internal reflection?

Answer 22

-happens when light goes into a substance with a lower refractive index (eg: glass into water into air)
-happens when the angle of in. is larger than the critical angle
-light will keep reflecting

Question 23

What is the Critical angle?

Answer 23

The angle of incidence which causes the angle of reflection to be 90º so that the light refracts onto the boundary
< c.a = reflection > c.a = refraction

Question 24

State an equation linking critical angle and refractive index (critical angle)

Answer 24

refractive index = 1/ sin(critical angle)
n = 1/ sin(c)

Question 25

What is the Refraction of sound?

Answer 25

-sound can also refract (change direction) when it travels to a different media
-sometimes, it can refract due to a change in temperature

Question 26

What is meant by “the doppler effect”

Answer 26

wave source is moving towards observer -> observed frequency increases and observed wavelength decreases and vv since v = f×λ and speed is constant
-if speaker and mic are getting closer = higher pitch
-if speaker and mic are getting further = low pitch

Question 27

State the equation for the period

Answer 27

T = 1/f

Question 28

Why would you sterilise food?

Answer 28

It kills microbes in it and it will stay fresh longer

Question 29

How do glass blocks affect the rays?

Answer 29

They usually:
-waves travel at different speeds in materials with diff. densities
-when a wave crosses a boundary into another medium the speed and direction change
-this is refraction