Reflection, Refraction and Diffraction Flashcards
What is Reflection?
When a straight wave is directed at a hard flat surface and is reflected at the same angle
How do we observe reflection?
By a light ray being directed at a mirror
What is Refraction?
When a wave passes between two media its wave speed changes (sometimes direction). Frequency remains constant
How do we show refraction?
Water waves crossing a boundary from deep to shallow (slower in shallow)
When light is directed at a glass block at an angle
What is diffraction?
When waves spread out after passing through a gap or round an obstacle
How do we show diffraction?
A ripple tank when straight waves are directed at a gap
narrow = more spread out
longer wavelength = more spread out
What is a diffraction grating?
A plate with many parallel slits in it
What is the equation for the angle that waves interfere constructively through each slit?
d x SinO = n x wavelength
d = distance between each pair of lines
O = angle
n = a whole number (order of maxium)
How does wavelength change the diffraction pattern?
As wavelength increases, the pattern becomes more spread out
What happens when a wave hits a boundary at 90 degrees?
The speed changes but the direction stays the same
Why does direction change when a wave hits a boundary at an angle?
The part that hits the boundary first changes speed first, causing direction to change
What is the equation for Refraction Index?
n = c/v n = refraction index c = speed of light in vacuum v = speed of light in medium
What is Snell’s Law?
n1SinO1 = n2SinO2 n = refraction index
What is the critical angle?
The precise angle at which total internal reflection can occur
What is the equation for critical angle?
SinC = 1/n
