Light: Introduction To
Light: Introduction To
Light: Introduction To
Light
as a wave
Dr Lisa Jardine-Wright
Cavendish Laboratory
What is a Wave?
Transverse
Longitudinal
Sound
• Longitudinal
• Mechanical
Examples of Waves
Ripples on a pond
• Transverse
• Mechanical
Examples of Waves
Light
• Transverse
• Electromagnetic
Wavelength, λ
• Distance before the wave repeats.
• Units are metres, m.
Frequency, f
• The number of whole waves that pass a fixed point
each second.
• Units are Hertz, Hz.
0.5 Hz
Describing Waves
Amplitude, a
• Maximum displacement of the wave.
Describing Waves
v=fxλ
The speed of a wave is only altered by
changing the medium through which it
travels.
• Speed of sound in air = 340 m/s
• Speed of sound in water ≈ 1500 m/s
Reflection & Refraction
Reflection
• angle of incidence = angle of reflection
θi θr
Reflection & Refraction
Reflection & Refraction
Refraction
Air Glass
Air
θt
θi
Interference & Diffraction
Interference
• Wave interference is what happens when two waves
meet while travelling along in the same medium.
Interference & Diffraction
Interference & Diffraction
Interference & Diffraction
Diffraction
• Is the spreading out of waves beyond openings and…
Interference & Diffraction
Diffraction
• and the bending of waves around obstacles
Interference & Diffraction
Light waves