Light And Sound Flashcards
Are light waves transverse or longitudinal ?
Transverse
What is reflection ?
Reflection is the process by which a ray of light strikes a Boundary and returns towards that source
What is refraction ?
Refraction is the bending of light as it travels from one medium to another. This bending occurs because the speed of the wave changes in different media
What is the diffraction ?
When light waves meet a gap in a barrier, they carry on through the gap. However the waves spread out to some extent into the area beyond the gap
What is the law of reflection ?
Angle of incidence equals angle of reflection
How do you draw rays of light ?
- they are straight lines
* they have arrows that indicate their direction
What is the normal ?
And imaginary line at a right angle to the Boundary
Where are angles always measured between ?
Ray and the normal, never between the ray and the boundary
What is the refractive index ?
How bendy the material is for light, as it tells you how much the speed of light changes through a material
What can the refractive index never be below ?
1
What is the equation for refractive index ?
Sin(angle of incidence)
Refractive index = ————–
Sin(angle of refraction)
What happens to light when it enters a material with a high refractive index ?
Light bends towards the normal
What happens to light when it enters a material with a lower refractive index ?
Light bends away from the normal
When does total internal reflection occur ?
This only happens in high to low refractive index, and beyond the critical angle
Equation for critical angle
1
Sin(C) = —-
n
Uses for total internal reflection
Optical fibres and can carry a enormous amount of information as pulses of light
Are soundwaves are longitudinal or transverse ?
Longitudinal
Can sound travel in a vacuum ?
No
How fast does sound travel in air ?
340m/s
What is the range of Hz that human can hear ?
20 to 20,000 Hz
What is on the X axis of oscilloscope ?
Time per division
What is on the Y axis on an oscilloscope ?
Voltage per division
How do you find frequency from an oscilloscope ?
- fine two points on the whole wave that are the same
- Measure the distance between them in divisions
- multiply the number of divisions by the timebase setting (X s/div) to get the period of the whole wave (T)
- F = 1/T
How do you find amplitude from an oscilloscope ?
- find the tallest point of the wave
- Measure the number of divisions above the centreline of this point
- multiply the number of divisions by the voltage setting (X v/div)
Describe analogue
Amplitude and/or frequency constantly vary
Describe digital
Consists of pulses with two states on-off.
What are the advantages of using digital rather than analogue ?
- Digital signals can carry more information as they have bigger bandwidth and multiplexing
- analogue signals my crackle lose signal as when analogue signals are amplified so can random signals picked up by waves
