Light and Sound

What is the thin lens formula?

“1/f = 1/di + 1/do”

• f = focal length of the lens

• do​ = object distance (from the lens)

• di​ = image distance (from the lens)

How is fraction the same as a ratio?

Yes! A fraction represents a ratio — it compares two quantities:

a/b = a:b

What is the relationship between wave speed, wavelength, and period?

"Waves travel: Length over Time!"
(Think: wavelength ÷ period)

What is myopia, and where are light rays focused?

Myopia (nearsightedness) is a condition where distant objects appear blurry because light rays are focused in front of the retina.

✅ Near objects can still be seen clearly.
❌ Distant objects are blurry.

How is myopia (nearsightedness) corrected?

Myopia is corrected using a divergent lens (also called a concave lens).

• This lens spreads out incoming light rays so they focus on the retina, rather than in front of it.

• Allows distant objects to appear clear again.

What is a diverging lens and how does it affect light?

A diverging lens, or concave lens, is a lens that spreads out (diverges) incoming parallel light rays.

What is dispersion in the context of waves (especially light)?

"Different colors, different speeds—light splits like a deck of cards!"

How does the frequency of light relate to its index of refraction and refraction amount?

Light with a higher frequency (shorter wavelength, like violet or blue) has a higher index of refraction in a material and therefore bends (refracts) more than lower-frequency light (like red).

What is chromatic aberration and what causes it?

Chromatic aberration is a type of optical distortion in lenses where different colors of light do not focus at the same point, causing blurry or color-fringed edges in images.

What is the relationship between a lens's power and its focal length?

“Fewer meters, more power!”
(Shorter focal length = stronger lens)

The power (P) of a lens is the inverse of its focal length (f) in meters:

P = 1/f

What is a diopter, and how is it defined?

“Diopters are just meters flipped!”

A diopter (D) is the unit of lens power, defined as the inverse of the focal length in meters:

1 diopter = 1/meter

When is optical power positive or negative?

“Converging = Positive power, Diverging = Negative power”

How do you find the combined optical power of multiple lenses in a system?

In a multi-lens system (with lenses placed close together), the total power is the sum of the individual powers:

Ptotal = P1 + P2 + P3 +…

How does air temperature affect the speed of sound?

“Heat up the air, sound gets there!”

“Cool it down, waves slow down.”