Random Double Stuff Flashcards
WAVES
difference between longitudinal and transverse waves
transverse = wave that vibrates perpendicular to the direction of the oscillation
e.g. light (EM Spectrum)
longitudinal = wave that vibrates parallel to the direction of the oscillation
e.g. sound
features of a transverse wave
all EM waves travel at same speed in _____ ______
free space
define wavefront
2 or more waves moving together have wavefronts, imaginary planes connect points on adjacent waves, vibrate together
define amplitude
maximum displacement of particles from their equilibrium position.
define wavelength
distance between a particular point on one cycle of the wave and the same point on the next cycle.
define frequency
number of waves passing a particular point per second. Is measured in Hertz (Hz).
define time period
time it takes for one complete wave to pass a particular point
waves transfer energy and information without transferring _______
matter
wavespeed =
wavelength x frequency
v = lamda x f
m/s = Hz x m
frequency =
1/time period
Explain the doppler Effect
When a car is not moving and its horn sounds, the sound waves we receive are a series of evenly spaced wavefronts.
If a car is moving, wavefronts of the sound are no longer evenly spaced.
Ahead of the car wavefronts are compressed as the car is moving in the same direction as the wavefronts. This creates a shorter wavelength and a higher frequency.
Behind the car wavefronts are more spread out as the car is moving away from the previous wavefronts. This creates a longer wavelength and a lower frequency.
properties of EM waves
Transfer energy
Are transverse waves
Travel at the speed of light in a vacuum
Can be reflected and refracted
features of a longitudinal wave
rarefactions and compressions
particles vibrate back and forth
do sound waves travel faster in solid than liquids, and faster in liquids than gases
yes
order of em waves from lowest to highest frequency
Radio Waves
Microwaves
Infrared (IR)
Visible Light
Ultraviolet (UV)
X – Rays
Gamma Rays
which has the shortest wavelength and has the lowest frequency
radio waves
which colour has the shortest wavelength and lowest frequency in the visible light spectrum
red
Uses of EM waves:
Radio Waves
Microwaves
Infrared (IR)
Visible Light
Ultraviolet (UV)
X – Rays
Gamma Rays
- radio waves: broadcasting and communications
- microwaves: cooking and satellite transmissions
- infrared: heaters and night vision equipment
- visible light: optical fibres and photography
- ultraviolet: fluorescent lamps
- x-rays: observing the internal structure of objects and materials, including for medical applications
- gamma rays: sterilising food and medical equipment.
risks of exposure to EM waves:
microwaves
infrared
ultraviolet
gamma rays
- microwaves: internal heating of body tissue
- infrared: skin burns
- ultraviolet: damage to surface cells and blindness
- gamma rays: leads to ionisation of cells causing mutation which might produce cancerous cells
How to reduce risks of:
UV
gamma
UV = stay in shade, sunglasses, sun cream
Gamma = led clothing, leave room - reduced exposure
explain journey of light ray from air into glass at angle and vice versa
Glass is denser than air, so a light ray passing from air into glass slows down. If the ray meets the boundary at an angle to the normal, it bends towards the normal.
A light ray speeds up as it passes from glass into air, and bends away from the normal by the same angle.
the denser the material, the ________ that light travels
slower (bends closer to normal)
practical: investigate the refraction of light, using rectangular blocks, semi-circular blocks and triangular prisms
- Set up your apparatus as shown in the diagram using a rectangular block.
- Shine the light ray through the glass block
- Use crosses to mark the path of the ray.
- Join up crosses with a ruler
- Draw on a normal where the ray enters the glass block
- Measure the angle of incidence and the angle of refraction and add these to your results table
- Comment on how the speed of the light has changed as the light moves between the mediums.
- Repeat this for different angles of incidence and different glass prisms.
refractive index =
n =
sin (angle of incidence) / sin (angle of refraction)
sin (i) / sin(r)
practical: investigate the refractive index of glass, using a glass block
- Set up your apparatus as shown in the diagram using a rectangular block.
- Shine the light ray through the glass block
- Use crosses to mark the path of the ray.
- Join up crosses with a ruler
- Draw on a normal where the ray enters the glass block
- Measure the angle of incidence and the angle of refraction and add these to your results table
- Calculate the refractive
index - Repeat steps 2 – 7 using
a different angle of
incidence - Find an average of your
results.
practical: investigate the refractive index of glass, using a glass block
- Set up your apparatus as shown in the diagram using a rectangular block.
- Shine the light ray through the glass block
- Use crosses to mark the path of the ray.
- Join up crosses with a ruler
- Draw on a normal where the ray enters the glass block
- Measure the angle of incidence and the angle of refraction and add these to your results table
- Calculate the refractive
index - Repeat steps 2 – 7 using
a different angle of
incidence - Find an average of your
results.
describe the role of total internal reflection in transmitting information along optical fibres and in prisms
optical fibres - use light to carry digital information over long distances
explain what is the critical angle and the 3 conditions
The angle of incidence which produces an angle of refraction of 90 (refracted ray is along the boundary of the surface).
When the angle of incidence is greater than the critical angle, total internal reflection occurs (all light is reflected at the boundary).
This effect only occurs at a boundary from a high refractive index material to a low refractive index material.
When the angle of incidence is lesser than the critical angle, light partially internally reflected
when the angle of incidence is equal to critical angle, lots of internal reflection and emerging ray along surface
DEFINE critical angle
the cirtical angle is the angle of incidence within an optically denser medium when the light is refracted at 90 degrees to normal
critical angle =
c =
sin ^-1 (1/n)
refractive index =
n =
1 / sin(c)
sound waves are longitudinal waves and light is transverse waves and both can be ______ and ______
reflected and refracted
frequency range for human hearing
20–20 000 Hz
ELECTRICITY
know the units for :
current =
charge =
resistance =
time =
potential difference =
power =
current = Ampere (A)
charge = coulomb (C)
resistance = ohm (Ω)
time = second (s)
potential difference = volt (V)
power = watt (W)
Explain how fuses protects the device or user in domestic appliances
Stop the flow of current by melting if the current is too high. So protecting sensitive components and people because if the components function at too higher temperature it can cause a fire.
Explain how circuit breakers protects the device or user in domestic appliances
breakers again break the circuit if current is too high.
Explain how insulation and double insulation protects the device or user in domestic appliances
prevent people from touching exposed wires and getting shocks.
Explain how earthing protects the device or user in domestic appliances
provides a low resistance path to the earth so if some one does come into contact with a current instead of flowing through them to the earth giving them a shock it flows through the earthing wire.
why a current in a resistor results in the electrical transfer of energy and an increase in temperature, and how this can be used in a variety of domestic contexts
Resistance causes transfer of electrical energy to heat energy. Some components are designed to have a high resistance to make sure this happens, for example electrical heaters that have lots of resistors to ensure a high resistance so a lot of heat is produced.
Power =
P =
(watts)
current x voltage
I x V
(A) x (V)
voltage =
energy transferred / charge
J/C
what is a volt equivalent to
Joule/coulomb
J/C
how to pick which fuse is correct when given
current of fuse should be slightly higher than current in circuit - so if circuit heats up normally and fuse keeps breaking even though current isn’t too high - then fuse current is too low
fuse amps (3A, 5A, 13A)
Energy (J) =
potential difference (V) x current (A) x Time (s)
I x V x t
Alternating current:
describe the motion of the current
current constantly changes direction
Direct current:
describe the motion of the current
current flows in only one direction
is mains eletricity AC or DC supply?
what voltage, frequency and current?
AC
230V
50Hz
do batteries and solar cells supply AC or DC electricity?
how much would a typical battery supply
DC
1.5 V
why a series or parallel circuit is more appropriate for particular applications, including domestic lighting
Advantages of parallel circuits:
Components (e.g. bulbs) may be switched on/off independently.
If one component breaks, current can still flow through the other parts of the circuit.
Bulbs maintain a similar brightness.
Advantages of series circuits:
Fewer wires, cheaper and easier to assemble.
Uses less power
as voltage increases in a circuit, current also________
increases
the more components in a circuit, the _______ the current
lower
describe graph of wire, filament lamp, diode as graph shows how current varies with voltage
(resistance changed using variable resistor)
wire - directly proportionate
filament lamp - s curve
diode - horizontal line and sudden steep gradient
changing resistance in a circuit will _________ the current
decrease as V = IR
describe how resistance changes in an LDR
as light increases, resistance decreases
describe how resistance changes in a thermistor
as temperature increases, resistance decreases
how to check if there is current in a circuit
add lamp, if current is flowing, lamp will light up
current is the ….
rate of flow of charge
so I =
Q/t
Q =
Charge (C) =
I x t