P5

Question 1

What is a satellite?

Answer 1

an object that orbits a planet in space, e.g the moon (natural) or an artificial satellite which has been put n space by humans

Question 2

What is the definition of gravity?

Answer 2

a universal force of attraction between masses

Question 3

What is the centripetal force?

Answer 3

this is the gravity the acts towards the centre of a circle

Question 4

What happens to the gravitational forces between objects when their distances are differed?

Answer 4

it gets weaker if the objects are moved further apart

- if the distance is doubled the force drops to 1/4 - this is called the inverse square law

Question 5

What happens to the speed of the planets in orbit due to their different distances?

Answer 5

• if they are close to the sun then their gravitational forces will be stronger resulting in their speed being fast
• if they are further away form the sun then their gravitational forces will be weaker resulting in their speed being slower

Question 6

How do comets travel in orbit?

Answer 6

• they have an oval like orbit which proves that when it comes closer to the sun it travels quicker due to the gravitational forces being stronger
• when they are further away from the sun they travel slower but are then pulled back towards the sun and the cycle starts again

Question 7

What is an ‘orbital period’?

Answer 7

the time it takes to make one satellite complete its orbit

Question 8

What can satellites in low polar orbit do/be used for?

Answer 8

• travel very quickly
• go around the earth several times each day
• they can be used to collect images of the earths surface
• weather forecasting
• military uses (e.g spying)

Question 9

What can geostationary satellites do/be used for?

Answer 9

• orbit much higher above earth
• take 24 hours to complete one orbit
• remain above a fixed position on the earths equator
• they can be used for communications (e.g satellite tv)
• weather forecasting

Question 10

What is suvat?

Answer 10

s = displacement
u = initial velocity
v = final velocity
a = acceleration
t = time

Question 11

What is the equation to find the final velocity?

Answer 11

v = u + at

Question 12

If 2 forces or velocities are acting at right angles on the same object, how do you work out the resultant force/velocity?

Answer 12

• by using Pythagoras theorem

Fr = (the square route of) F1 squared + F2 squared

Question 13

What is the definition for trajectory?

Answer 13

the path that a projectile takes

Question 14

What are the 2 velocities that are involved with projectiles?

Answer 14

• horizontal velocity

- vertical velocity

Question 15

What is parabolic trajectory?

Answer 15

when the object follows a downward curving path due to the earths pull of gravity

Question 16

What is the resultant velocity?

Answer 16

the sum of the horizontal velocity and the vertical velocity

Question 17

What impact does acceleration have on the horizontal and vertical velocities direction?

Answer 17

acceleration has no impact on the horizontal velocity, it can only affect the vertical velocity due to the gravity on earth

Question 18

What is the definition for acceleration?

Answer 18

the rate of change of an objects velocity over time

Question 19

What is the definition of pressure?

Answer 19

a force per unit area

Question 20

What happens when the temperature of a gas container is increased?

Answer 20

• the particles gain energy
• with increases kinetic energy the particles move more quickly
• each particle will collide with the walls of the container more frequently and they will collide with more force
• the pressure inside the container increases

Question 21

What is the equation for a collision of cars?

Answer 21

m1u1 + m2u2 = (m1 + m2)v

m1 being momentum from the first car
m2 being momentum from the second car
u1 being initial velocity from the first car
u2 being initial velocity from the second car
v being final velocity

Question 22

What is the typical wavelength of radio waves?

Answer 22

1m-10km

Question 23

What frequencies can pass through the atmosphere?

Answer 23

short wavelength - between 30MHz and 30GHz

Question 24

What frequencies can be reduced in strength or even stopped by the atmosphere?

Answer 24

above 30GHz

Question 25

What frequencies are reflected by the ionosphere?

Answer 25

below 30MHz

Question 26

Why are radio waves refracted as they pass through the ionosphere?

Answer 26

because they change velocity wen they move through ionized gas

Question 27

What kind of wave is light?

Answer 27

transverse wave because it is an electromagnetic wave

Question 28

What is reinforcement? (also known as constructive interference)

Answer 28

when the waves are in phase causing them to make larger amplitudes and therefor increasing the sound/light

Question 29

What is cancellation? (also known as destructive interference)

Answer 29

when the waves are out of phase meaning their resulting amplitude is 0 which means that the waves cancel eachother out - dark light is made/no or quiet sound is made

Question 30

What does path difference mean?

Answer 30

the path difference is when 2 waves coming from the same source take different paths to get to the same object - for example, one wave could reflect off a mirror whilst the other could take the direct route to the object

Question 31

What will the path difference be for destructive interference?

Answer 31

an odd number of half wavelength

Question 32

What will the path difference be for constructive interference?

Answer 32

an even number of half wavelength

Question 33

What does the term oscillator mean?

Answer 33

it means the central point of, in this case, a wave

Question 34

What happens if the thing a wave is trying to get through is only horizontally polarized?

Answer 34

then the wave will have to move in that direction to get through the polariser

Question 35

What is the definition of a medium?

Answer 35

a substance that waves can travel through

Question 36

When/where does refraction occur? Why does it cause the wave to change direction?

Answer 36

refraction occurs at the boundary between two media, this is because when a wave travels through one medium into another it slows down as it travels through the different densities and therefor changes direction - it changes direction because when it has time to slow down after going through a different medium, it bends more towards the 'normal' (an 90degree angle to the medium) cause a smaller angle of refraction

Question 37

What is a refractive index?

Answer 37

a measure of how much the medium refracts (bends) light rays as they cross the boundary

Question 38

How do you calculate the refractive index?

Answer 38

refractive index = speed of light in a vacuum / speed of light in a medium

Question 39

What is an example of something with a high refractive index? Why?

Answer 39

a diamond - because all light that shines on the diamond at an angle greater than 24.4 degreed will undergo total internal reflection (this is what produces the sparkling effect)

Question 40

What is the critical angle?

Answer 40

the maximum angle of incidence before total internal reflection happens

Question 41

What happens when white light travels through a prism? Why?

Answer 41

it refracts, however this refraction causes all the lights on the spectrum to show - this happens because when white light is refracted it is separated due to the different colours' refractive abilities, e.g blue/violet light is slowed down the most when changing its medium and therefor it is refracted a great amount whereas red light isn't refracted as much as it doesn't slow down that much - this happens because the different colours have different wavelengths, e.g red has a longer wavelength and blue and violet have shorter wavelengths meaning they diffract at different speeds

Question 42

What is it called when white light is refracted to show the colours in the spectrum?

Answer 42

dispersion

Question 43

What is a convex lens?

Answer 43

this is a converging lens which means that the light rays that pass through it they meet at a focus

Question 44

What does the term 'focal length' mean?

Answer 44

the distance between the centre of the lens and the focal point

Question 45

What does the term 'focal point' mean?

Answer 45

where all the light rays meet up behind the lens

Question 46

What is the difference between thin and fatter convex lenses?

Answer 46

thin convex lenses don't refract as much as fatter lenses which means that the focal length wont be as long

Question 47

What is the optical centre?

Answer 47

the centre of the lens

Question 48

What happens if the beam of light is parallel to the optical centre?

Answer 48

it will pass through the focal point

Question 49

What happens if a diverging beam of light travels through a convex lens?

Answer 49

it will converge after it passes through the lens but it will not hit the focal point

Question 50

What is the difference between real images and virtual images?

Answer 50

real images can be projected onto a screen and are always upside down (inverted) whereas virtual images cannot be projected onto a screen because they are the right way up

Question 51

What does the term magnification mean?

Answer 51

a measure of how much bigger the image is than the object