Physics II - Exam 3: Diffraction & Interference of Light

Diffraction

when a wave bends or warps around an obstacle, or spreads out through an opening

When is diffraction most noticable?

when the wavelength of light is equal to or larger than an opening

When light goes through a wide opening, ____ diffraction results

little

When light goes through a narrow opening, _____ diffraction results.

lots

Why do you only need one subwoofer for home theater, but many little speakers?

low frequency bass notes diffract to all points of the room, but high frequencies come straight out, requiring multiple speakers for even coverage

Why are high frequency speakers shaped like horns?

because high frequencies come straight out and need additional assistance to disperse sounds

Why do we experience diffraction of sound much more than the diffraction of light?

because diffraction depends on wavelength and the wavelength of sound is about a million times larger than the wavelength of light. This means sound waves can bend around obstacles and spread out more effectively than light waves.

A wider slit means the pattern of fringes will be _____.

narrower

A longer wavelength means the pattern of fringes will be ____.

wider (longer wavelengths diffract more)

Diffraction equation for the dark fringes in light diffracting through a single slit:

Wsinθ=mλ

• W= width of slit

• θ= angle

• m= order of the fringe (an integer)

• λ= wavelength

What is the significance of the equation: Wsinθ=mλ ?

This equation is fundamental in understanding how light behaves as it passes through a slit, leading to the formation of dark and light patterns on a screen.

Interference

when waves (light, sound, water) interact constructively or de-constructively

How can two lights make darkness?

light waves cancel between bright spots

Interference equation involving the condition for bright spots:

dsinθ = mλ

• d= distance between slits

• θ= angle from center axis to mth spot

• m= the integer representing the order of the bright fringe

• λ= wavelength of the light.

What is the significance of this equation: dsinθ = mλ ?

It describes the condition for constructive interference at specific angles, resulting in bright fringes in a diffraction pattern.

Holograms are ____ pictures.

not

What are holograms?

frozen records of interference patterns (of light) that create three-dimensional images

What do holograms do?

they record the way an object messes up light by creating interference patterns that can later reconstruct the light waves.

Can you see around corners of a hologram?

yes