Things I Need To Know Flashcards Preview

Physics GCSE > Things I Need To Know > Flashcards

Flashcards in Things I Need To Know Deck (53)
Loading flashcards...
1
Q

Pressure for gas at a fixed volume

A

P1/T1 = P2/T2
Where temp is kelvins
•C = k + 273

2
Q

Equation for power

A

P = IV

3
Q

Equation for energy

A
E = IVT
E = PT
4
Q

Equation for charge

A

Q = IT

5
Q

Equation for voltage

A

V = IR

6
Q

Equation for wavespeed

A

Wave speed = frequency x wavelength

7
Q

Equation for frequency

A

Frequency = 1/T

8
Q

Equation for refractive index

A

N = sin(I)/sin(r)

9
Q

Equation for critical angle

A

Sin(C) = 1/n

10
Q

Equation for word done

A

W = fd

What fuck dat

11
Q

Equation for GPE

A

GPE = mgh

12
Q

Equation for KE

A

KE = 1/2mv^

13
Q

Equation for density

A

Density = mass/volume

14
Q

Equation for pressure

A

Pressure = force/area

15
Q

Equation for pressure difference

A

P = height x density x g

16
Q

What happens to a ray of light travelling inside a prism?

A

Total internal reflection because the angle of incidence is greater than the critical angle.

17
Q

What happens when light enters a rectangular glass block?

A

It would refract towards the normal but carry on outside the block with the same direction and angle as before.

18
Q

What is total internal reflection?

A

When light passes from an optically more dense medium to an optically less dense medium, for example from glass to air, the majority of the light is refracted away but there is a small amount that is reflected from the boundary.

19
Q

Draw a ray of light hitting the centre of a glass block

A

It hits it at an angle and reflects it at 90• so it is always totally internally reflected.

20
Q

What is the critical angle and what does it have to do with reflection?

A

As the angle of incidence in the more dense medium increase the angl do refracting does so too until it reaches the critical angle which is 90•. The reflected ray is still weak.

21
Q

What happens when the angle of incidence in a more optically dense medium is past the critical angle?

A

ALL of the light is reflected from the boundary and the ray has undergone TOTAL internal reflection.

22
Q

What does the value of the critical angle depend on?

A

The density of the medium.

23
Q

How does a periscope work?

A

The angle of incidence is 45 which is greater than the critical angle for glass which is 42 so the light is totally internally reflected off the first prism to the next prism then to the direction that it was originally travelling.

24
Q

How does the optical fibre work? How are they designed specially for TIR?

A

Very thin strand made of two types of glass. Inner layer is the more optically dense one. The fibres are narrow ensuring LIGHT always enters at an angle greater than the critical angle. No light escapes across the boundary emitting an image on the other end. Used in bundles.

25
Q

Endoscope use of TIR

A

Endoscopes are used to see inside the body for example to examine the stomach. Light travels down and illuminates the object to be viewed.

26
Q

Optical fibres in technology?

A

Telecommunications use copper wires to transmit messages which are converted from electrical to light then to electrical on the other end by a light sensitive detector.

27
Q

What is the a spectrum?

A

The band of colours that form when white light passes through a prism because each colour travels through at a slightly different speed.

28
Q

What is dispersion?

A

Each colour emerges out of the prism in a slightly different direction.

29
Q

Order of the spectrum from lower to huger deviation?

A
Richard  RED
Of          ORANGE
York       YELLOW
Gave      GREEN
Battle     BLUE
In            INDIGO
Vain        VIOLET
30
Q

What happens to the speed, frequency and wavelength of light as it enters a prism?

A

Speed decreases
Frequency stays the same
Wavelength decreases

31
Q

What is the range of frequencies humans can hear?

A

20Hz to 20,000Hz

32
Q

Describe the stages involved in turning chemical energy into electrical energy.

A

Coal is burned at a power station releasing chemical energy as thermal energy and heating up water which becomes steam which has elastic potential energy which rises and spins a turbine which now has kinetic energy which in turn spins a generator and a magnet and electricity is generated.

33
Q

Rank five ways energy can be lost in a house in decreasing order.

A

Windows, roof, walls, floor, door

34
Q

How does double glazing reduce the loss of thermal energy through windows?

A

When hotter gas molecules hit the glass the trapped air, as it is a poor conductor, prevents conduction or convection through the outside pane of glass

35
Q

Equation for power

A

Work done/Time taken

36
Q

What material would you used on the inside/outside of your walls?

A

Outside: bricks, good insulator but strong with good weathering properties.
Inside: good insulator but don’t need to be as strong, cheaper and easier to be built with thermal bricks.

37
Q

Pressure for has at a fixed temp

A

P1/p2 = v1/v2

38
Q

Difference between a fixed and a variable resistor?

A

You can alter the size of the resistance In a variable resistor but it is not in a fixed resistor.

39
Q

What does the variable resistor act like in a circuit?

A

A dimmer switch as the more resistance the less current will flow and the bulb will glow less brightly.

40
Q

What is a thermistor?

A

A resistor where the resistance changes dramatically with temperature. If the temperature is increased the resistance drops. Used in temperature sensitive circuits.

41
Q

How do diodes work?

A

Ensure current flows through them one way as it has a low resistance on that sight but it has a very high resistance if the current wants to flow the other way.

42
Q

How to measure resistance in a circuit

A

You need: (from negative to positive, left to right)
A switch
A voltmeter in parallel to a piece of wire
An ammeter
A variable resistor
Close the switch and record the readings of the ammeter and voltmeter. Change the resistance with the variable resistor and add the new values of voltage and current. Repeat the whole process at least times. Results are put into a table then graph.

43
Q

What should the graph of current and voltage look like according to who’s law,

A

If the temperature of the wire was constant it should be a straight line through the origin as they are proportional according to Ohms law.

44
Q

What happens to the current voltage graph with larger currents?

A

The wire becomes warm and at first the graphics still proportionate but when the temperature rises the resistance increases so it bends over.

45
Q

What is a comet?

A

An icy mud ball that orbits the sun in an elliptical orbit.

46
Q

How would you investigate how the extension of a steel spring changes?

A

You have a clamp stand with a clamp and a spring on it and you add 1N weights on it and measure with a ruler that’s held up by another stand the extension of the spring. Continue this and you should see that the extension is equal to the load force UNTIL the spring reaches elastic limit.

47
Q

What is electomagnetic induction

A

If a wire moves across a magnetic field at right angles a voltage is generated in the wire.

48
Q

What happens to waves when the depth of water changes?

A

Their wavelength becomes shorter but the frequency is the same so waves are traveling more slowly in shallower water

49
Q

What is diffraction?

A

When a wave is passing through a barrier with a large gap most of the waves go in the same direction but to the left and right of the gap there are no waves. If the barrier is the same size as the wavelength the waves spread out.

50
Q

How can you use infrared with night vision goggles?

A

As the hotter an object is the more infrared it emits cameras designed to detect infrared can detect objects that have heat even in the absence of visible night.

51
Q

why does a light ray change direction when it passes from air to glass?

A

Glass is more sense than air so the light way bends towards the normal. The angle of refraction is less than the angle of incidence.

52
Q

How do fluorescent lamps work?

A

Mercury vapour inside a tube gives off UV rays when a current is passed through it. When the UV light strikes the fluorescent powder coating the tube white light is given out.

53
Q

Describe an experiential to investigate the redaction of light using rectangular, semicircular blocks and triangular blocks.

A

When a ray of light travels from one transparent substance to another one with different optical density it changes direction.