Waves 2 Flashcards
Why do waves travel faster in solids
Molecules closer. Less time for energy transfer
Ultrasound waves
Higher than 20,000 Hz
How are ultrasound waves used to find distances
Ultrasound waves are partially reflected when they meet a boundary between two different media. The time taken for the reflections to reach a detector can be used to determine how far away such a boundary is. This has applications in SONAR, echolocation (for example with bats) and medical ultrasound scans.
P waves
Primary waves
Longitudinal
Can travel through liquids
S waves
Secondary waves
Transverse
Absorbed by liquids
Shadow zones
What is used to detect earthquakes
Seismometer
How can seismometer traces be
used to determine the distance between a detector and the earthquake?
The P-waves (primary waves) arrive before the S-waves (secondary waves). If scientists already know the speed of both types of wave, then the difference in arrival time can be used to calculate the distance travelled from the same point (focus of the earthquake).
How is the epicentre of an earthquake found
Triangulation from 3 detectors
How do we know the core is liquid
S-waves cannot travel through liquids. Shadow zones exist on the crust where S-waves are not detected but P-waves are. This suggests that there is a liquid layer within the Earth that the S-waves are not penetrating.
What are EM waves
Transverse
EM waves order
Raging Martians Invaded Venus Using X-ray Guns
EM waves speed
300,000,000 m/s
Units for radiation dose
Sieverts (Sv). Radiation dose is a measure of the risk of harm resulting from an exposure of the body to the radiation.
UV danger
Ultraviolet waves can cause skin to age prematurely and increase the risk of skin cancer.
X-ray / gamma danger
X-rays and gamma rays are ionising radiation that can cause the mutation of genes and cancer.
What do hot objects do
All objects emit and absorb infrared radiation. More hot = more infrared emited
What is a perfect black object
Absorbs all radiation. It would also be a perfect emmitter.
Emission of object at constant temperature
An object that has a constant temperature emits radiation across a continuous range of wavelengths.
When do objects increase in temperature
When it absorbs radiation faster than it is emitted
What is the greenhouse effect
Gases in the atmosphere prevent energy from leaving the planet once it has been emitted from the surface (either via absorption or reflection back down to the surface). Because of this, not as much energy is emitted from the planet as is transferred from the Sun and the planet warms up.
