Combined Waves Topic Vocabulary Flashcards
Angle of reflection
the angle between the reflected ray and the normal

Angle of incidence
the angle between the normal and the incident ray

Angle of refraction
the angle between the refracted ray and the normal

Snell’s Law
when an incident ray passes into a material: n = sin i ÷ sin r
Law of reflection
in reflection at a surface, the angle of incidence is equal to the angle of reflection

Diffraction of waves
when waves meet a gap in a barrier, they carry on through the gap, but the waves spread out to some extent into the area beyond the gap

Dispersion of white light
when white light passes through a prism, it splits into different spectral colours and wave lengths (dispersion) and the different colours of the spectrum seperate

Refraction
light waves change speed when they pass across the boundary between two differenct media
this causes them to change direction

Reflection
there is reflection when waves bounce off a surface

Real image
produced when real rays of light cross and can be projected
Virtual image
produced when virtual rays of light cross
can’t be projected
it is the same size, laterally inverted and the same distance beyond the mirror as the real image
Transverse Wave
produced when the vibrations are perpendicular to the direction of energy
e.g. light waves
Longitudinal wave
produced when the vibrations are parallel to the direction of energy
e.g. sound waves
Refractive index
refractive index (n) = speed of light in air (3x108) ÷ speed of light in material
The electromagnetic spectrum
a continuous range of wavelengths

Frequency
the number of vibrations (or waves) per second in Hertz (Hz)
Wavelength
the shortest distance between two parts of a wave that are in phase (doing the same thing)

Amplitude
the distance from the centre of a wave to the peak or trough

Speed of light
the distance light can travel in a unit of time through a given substance
Speed of light in air
3x108 m/s
Speed of sound in air
343 m/s
Echo
a sound caused by the reflection of sound waves from a surface back to the listener
Ultrasound
sound with a frequency greater than 20,000Hz (20 kHz)
this is above the range of human hearing
Reliability
a set of results that are repeated and the spread of the readings is small (or they cluster together)
Validity
an experiment is valid if you measured what you set out to investigate
Fair test
a test in which only the independent variable has been allowed to affect the dependent variable e.g. by keeping all other variables constant
Parallax error
caused by not having the eye in line with the object being measured and the scale being measured against
Human error
humans making small mistakes when taking readings
this can be minimised by good experimental technique and repeating readings
Random error
produced either side of the true value
caused by human error or unknown and unpredictable changes in the experiment (e.g. measuring instruments or in the environmental conditions)
Precision
the result of using the correct piece of equipment with appropriate resolution or smallest division
precise measurement are ones in which there is very little spread about the mean value
Accuracy
reliable and precise measurements can produce results very close to the true value and therefore be accurate