Properties of Waves, Wave Behaviour , Superposition

What is a wave? (3)

The transfer of energy from one place to another without permanently transporting matter

What is a transverse wave?

A wave that oscillates matter in a perpendicular direction to the wave’s motion (or propagation)

ex.

• string in musical instruments

• wave dance move

• moving slinky in up and down motion

• water

• EM waves/ light

What is a longitudinal wave?

A wave that oscillates matter in a parallel direction to the wave’s motion (or propagation)

ex.

• sound oscillation of air molecules

• pushing sling back and forth

• earthquake motion

What is a mechanical wave?

A wave that requires a medium to move through or else it cannot exist.

• Can be transverse or longitudinal

ex.

• waves in the ocean (need water, the medium, to occur)

What are electromagnetic (EM) waves? (3)

A wave that moves through a vacuum (which is just empty space).

• Created as a result of vibrations between electric and magnetic fields.

• ALL EM waves are photons and move at the same speed (3 ×10⁸ ms^-1)

What is the electromagnetic spectrum?

A classification of the types of electromagnetic waves arranged by wavelength and frequency.

• Gamma rays, X rays, Ultraviolet, visible spectrum, Infrared, Microwave, Radio waves

What are the 8 components of a wave?

• cycle

• period (T)

• frequency (f)

• amplitude (A)

• wavelength (λ)

• crest

• through

• equilibrium position

What is a cycle?

One complete shape that starts and end at the same position (e.g. crest to crest)

What is is the period (T)?

The amount of time it takes for the cycle to occur.

• measured in seconds (s)

What is the frequency (f)?

The amount of cycles that occur per second.

• measured in Hertz (Hz)

• 1 Hz = 1 cycle/ second

What is the relationship between period and frequency?

• T = time/ cycle

• f = cycle/ second

T = 1/f and f = 1/T (reciprocal relationship)

What is the amplitude (A)?

The maximum distance a particle moves from the the equilibrium position.

What is a wavelength (λ)?

The distance a cycle travels.

• measured in meter (m)

What are crest, throughs, and equilibrium position?

• Crest - highest point

• Through - lowest point

• Equilibrium position - central rest point when not disturbed by wave

What is compression and rarefaction?

Occurs in longitudinal waves and corresponds to the crests and throughs respectively of the wave.

• Length between 2 consecutive crests or throughs is the wavelength

What is the universal wave equation?

v = f λ = λ/T

where v is velocity

What does in phase and out of phase mean?

• In phase - particles are aligned and move insync

• Out of phase - particles are not aligned (mismatched)

What is the law of reflection?

Reflection is when light bounces off surfaces.

• θ_i = θ_r

What is the angle of incidence (θ_i) and angle of reflection (θ_r)?

• Angle of incidence (θ_i) - the angle between the incoming (or incident) ray and the normal

• Angle of reflection (θ_r) - the angle between the reflected and the normal

What is the law of refraction (aka snell’s law)?

Refraction occurs when light enters a new medium, causing its path to be bent as a result of the change in speed.

What is the equation for Snell’s law?

n₁ sin θ₁ = n₂ sin θ₂

What is the index of refraction (n)?

• Dimensionless number

• Tells us how much light slows down (or how much a material reduces the speed of light compared to vacuum) and bends upon entering a new material

What is the equation for the index of refraction?

n = c/v

• c = speed of light in a vacuum (3×10⁸ ms^-1)

• v = speed of light in a material

Note: the index of refraction must be greater than or equal to 1

What happens to the angle of refraction and speed of the light when it travels from a high to a low index of refraction?

• The angle of refraction is further from the normal or appears fat

• The speed of light in the medium is faster

What happens to the angle of refraction and speed of the light when it travels from a low to a high index of refraction?

• The angle of refraction is closer to the normal or appears smaller

• The speed of light in the medium is slower

What happens when a wave enters a new medium?

• The frequency remains the same (at that transition point, the rate of oscillation must be the same here)

• The velocity and wavelength change

What happens if your calculator gives “error” for for snell law question?

“error” indicates that the angle is beyond the critical angle, and the ray is reflected.

• Note: refraction in denser to less dense mediums occurs when the angle of incidence is less than the critical angle

What are wavefronts?

• A set of locations in a medium where the wave is in phase

• The length between the 2 lines of a wavefront is exactly one wavelength

• Represented by evenly spaced lines and which are perpendicular to the ray’s propagation

• May come in different shapes depending on the movement of the wave (e.g. left to right, outward in all directions)

What is the law of diffraction?

Idk honestly

What is the principle of superposition?

• Occurs when waves are in the same physical location (overlapping each other) in the medium through which they move in

• The amplitudes add together

• Continue to move in the direction they were originally travelling in

What is constructive interference?

Two amplitudes in the same direction adding to produce one large amplitude

What is destructive interference?

Two amplitudes in the opposite direction cancelling each other out to produce a smaller or no amplitude

How can wavefronts show constructive and destructive interference?

• Constructive interference: When two waves are perfectly in phase (on top of each other)

• Destructive interference: When two waves are perfectly out of phase (in between each other

What happens when a pulse hits a fixed point?

It gets reflected backwards and its amplitude flips upsedown

What happens when a pulse hits a free point?

It gets reflected backwards and amplitude is not flipped