Physics Flashcards
Describe what happens to wasted energy in energy transfers
Wasted energy is dissipated to the surroundings - usually as thermal energy due to friction.
Explain some ways in which energy is transferred wastefully by mechanical processes.
During a mechanical process, energy is often wasted as thermal energy. This is due to friction, which generates this thermal energy - this is wasteful.
How can we reduce wasted energy?
Lubrication, to reduce friction
Insulation, e.g to reduce heat escaping from a house
How do you calculate wave speed?
frequency x wavelength
Describe the differences between transverse waves and longitudinal waves
In transverse waves, particles vibrate at right angles to the direction of wave travel. Whereas, in longitudinal waves, particles vibrate parallel to the direction of wave travel.
Give examples of transverse waves
EM Waves
Seismic S waves
Give examples of longitudinal waves
Sound waves
Seismic P waves
Describe differences in the ways parts of the EM spectrum are absorbed / transmitted
Visible light is absorbed by dark objects
Some EM radiation, eg UV radiation, is absorbed by the atmosphere.
Describe why radio waves have a longer range than microwaves
Radiowaves have a much longer range as they are refracted in the ionosphere. This means that it can move around the Earth’s curved surface, without having to reflect of a satellite.
Whereas, microwaves aren’t refracted in the ionosphere, so to travel around the Earth they have to be reflected off a satellite.
Explain what background radiation is.
Ionising radiation that is around us all the time from a number of sources.
List some sources of background radiation
Radon Gas Medical Cosmic Rays Buildings Food and Drink Nuclear
Describe how a Geiger-Muller tube works
Radiation passing through the tube ionises gas inside it and allows a short pulse of current to flow. A GM tube can be connected to a counter, to count the pulses of current or the GM tube may give a click each time radiation is detected.
Describe the process of B- and B+ decay
B- : In B- decay, an electron is emitted at high speeds from the nucleus. This is because a neutron has become a proton and an electron. Atomic number increases by 1, mass number stays the same
B+: In B+ decay, a positron is emitted at high speeds from the nucleus. A proton becomes a positron and a neutron. Atomic number decreases by 1, mass number stays the same.
What happens during nuclear rearrangement after radioactive decay?
After radioactive decay, the nucleus has a lot of excess energy. It then loses this energy by emitting a high-energy gamma ray.
What is half-life?
The amount of time taken for half of the radioactive nuclei in a sample of radioactive material to decay.
What is the power of a lens?
A measure of how much the lens bends light rays passing through it. A more powerful lens bends rays more and has a shorter focal length.
How do you calculate the power of a lens?
1/focal length
What is the units for power?
dioptre
Describe how the direction of a wave can change when moving into a different material
When moving into a new material, the wave can bend towards or away from the normal line.
Explain some effects of refraction of light in terms of changing speeds
When moving into a more dense material, waves slow down, causing them to bend towards the normal line.
Whereas, when moving into a less dense medium, waves speed up causing them to refract away from the normal line.
Describe what total internal reflection is
The reflection of a ray of light inside a medium when it reaches an interface
What is the critical angle?
The angle of incidence which causes the angle of refraction to be 90 degrees, running along the boundary.
Describe how ideas about the Solar System’s structure has changed over time
Ptolemy’s geocentric model - the idea that all planets revolved around us. They made observations using the eye and what they could see.
Copernicus introduced the heliocentric model.
Galileo then used the new telescope to discover 4 of Jupiter’s moons, plotting their movements to show that not everything revolved around the Earth.
Heliocentric model was now the widely accepted model.
Describe how methods of observing the Universe has changed over time
At first, in Ptolemy’s time, observations were made using the naked eye.
The invention of the telescope allowed scientists to see objects in space in greater detail.
Photography allowed astronomers to make more detailed observations and measurements than were possible by drawings.
Furthermore, telescopes in orbit around the Earth gave us much clearer images and allowed us to detect different types of EM radiation that may have been absorbed by our atmosphere
