Physics Flashcards
(28 cards)
What is a universe?
A large collection of billions of galaxies
What is a galaxy?
A large collection of billions of stars
Explain how a falling object can reach terminal velocity.
- Object initially has weight so it accelerates down
- There is drag which increases as speed increases
- Eventually drag = weight
- Therefore resultant force is zero and object travels at constant speed
What is Hooke’s law?
Force is directly proportional to extension, up to the limit of proportionality
What is power?
The amount of energy transferred per second
Define current.
The rate of flow of charge
Why does current in a resistor produce heat energy?
Resistors contain an ionic lattice which electrons collide with and this transfers heat which dissipates into the surroundings.
Explain why someone would hear a higher pitched sound when a noise moves towards them.
- The wavefronts bunch up which decreases the wavelength
- Which creates a higher frequency
- Which appears as a higher pitch
What is the same for all the types of waves in the EM spectrum?
- They all travel at the speed of light
- They can all travel through a vacuum
- They are all transverse
What is the order of the EM spectrum?
Radio - Micro - Infrared - Visible - UV - X-ray - Gamma
As wavelength increases what happens to colour?
It gets redder. Violet (low) -> Red (high)
What are the uses of the EM spectrum?
Radio - Broadcasting + communication
Microwaves - Cooking + satellite transmissions
Infrared - Heaters + night vision equipment
Visible - Optical fibres + photography
Ultraviolet - Fluorescent lamps
X-rays - Looking at the internal structure of objects
Gamma - Sterilising medical equipment
What are the dangers of the EM spectrum?
Micro - Internal heating of body tissue
Infrared - Skin burns
Visible - Damage to the retina
Ultraviolet - Damage to surface cells + blindness
X-Rays - Cell mutation
Gamma - Cancer + cell mutation
What are some protective measures to the dangers of EM waves?
Sun cream and lead shielding
Describe an experiment to investigate the refraction of light in a glass block.
- Place block on paper and draw around it
- Mark the position of the incident and emergent rays
- Remove the block and draw the refracted ray
- Measure angle i and r to the normal line
- Repeat for a range of values of i
- Make a graph of sin i against sin r
- Gradient gives refractive index
What is the critical angle?
The angle of incidence, above which, total internal reflection occurs
What are the conditions for TIR to occur?
- Denser to less dense medium
- i > c
How can coils of wire acting as a solenoid be made stronger?
- Increase number of turns in coil
- Increase current through coil
- Adding an iron core through the coil
Explain the motor effect.
- There is a current carrying wire/coil
- Which induces a magnetic field
- Which interacts with the magnetic field of the magnets
- Therefore it induces a force and the wire/coil rotates
Explain how loudspeakers work.
- A.C. changes current’s direction continuously
- Current in coil produces alternating magnetic field
- Producing force on the coil/cone
- Reversing direction of the current, reverses the direction of force
- So coil/cone vibrates
- And cone vibrates air particles which produces sound
What are the factors that affect induced voltage?
- Velocity of coil and magnet
- Strength of magnet
- Number of turns on coil
What are the ways in which we can reduce the risk of radiation?
- Keeping radioactive substances in shielded containers such as lead-lined boxes
- Wearing protective clothing to reduce contamination
- Limiting exposure time
- Handling radioactive substances with tongs to increase distance from them
- Monitoring exposure time with detector badges
What are the dangers of ionising radiation?
- Cell mutations
- Damage to cells and tissues
What is the moderator and what is its role in nuclear fission reactors?
Water or graphite cores that slow down neutrons so that they are slow enough to be absorbed again
