P6: Waves (triple) Flashcards
What happens to the particles in a medium when a wave passed through them?
The particles oscillate and transfer energy between each other.
What is the amplitude if a wave?
The maximum displacement of a point on a wave from its undisturbed point
What is the frequency of a wave?
The amount of complete waves passing a certain point per second.
What is the period on a wave?
The amount of time it takes for a full cycle of the wave.
Describe absorption of electromagnetic waves.
The wave transfers energy into the materials energy store which is mostly thermal.
Describe the transmission of waves.
The wave carries on travelling through the material. This often leads to refraction.
Describe the reflection of waves.
The wave is sent back on collision with a material.
Why can electromagnetic wave travel through a vacuum?
The are vibrations of electric and magnetic fields, not vibrations of particles. There are no particles in a vacuum.
What are the 7 basic types of waves in the electromagnetic spectrum?
Radio waves Micro waves Infrared Visible light Ultra violet X-rays Gamma rays
What happens to light when it travels through a denser medium.
It refracts towards the normal.
What happens to light when it travels through a less dense medium?
It refracts away from the normal.
How are radio waves produced for TV and radio?
Using an alternating current in a circuit. The object which charges oscillates to create the radio waves is called a transmitter.
How are radio waves received?
The incoming radio waves reach a receiver. The energy is transferred into the material of the receiver. The electrons oscillate generating an alternating current in a complete circuit. This current has the same frequency as the radio wave.
Describe how long-wave radio signals travel?
They diffract (bend) around the world and diffract around hills and into tunnels.
Describe how short-wave radio signals travel around the world?
They reflect from the ions sphere.
Which 3 electromagnetic waves can be harmful to people?
High frequency waves:
UV
X-rays
Gamma rays
Why are x-rays and gamma rays dangerous?
They can ionise atoms causing gene mutation or cell destruction and cancer.
What is a sievert?
A measure for radiation dose. Most uses only require millisieverts.
Describe the results of specular reflection.
when the rays are reflected in a singular direction. (smooth surface)
Describe the results of diffuse reflection.
when the rays are reflected in scattered directions. (rough surface)
What effect does a convex lens have on light rays parallel to its axis?
they are brought together (converge)
What effect does a concave lens have on light rays parallel to its axis?
they spread out (diverge)
Why do objects appear specific colours in visible light?
when the visible light hits the object, only specific wavelengths of light are reflected. this determines the colour. all the other wave lengths are absorbed by the object.
What are black bodies?
objects that absorb all the radiation that hit them.
What is the minimum frequency fro ultrasound?
20000Hz
How can ultrasound be used to observe a fetus?
some of the waves are reflected off of the fetus and these are timed by a computer to create an image of the fetus.
How can ultrasound be used to find flaws in materials and objects?
cracks in the material cause the waves to refract early so can be differentiated and recorded to find the imperfection.
What are seismic waves caused by?
Earthquakes or explosions
