Test Your Knowledge: Light and Optics

Every substance produces a different color (wavelength) of light when burned.

True ? When a substance is burned it gives off a characteristic wavelength of light that can be used to determine its composition through a process called grating spectroscopy.

When we look at another distant star system we are seeing a delayed image of it.

True ? Light does not possess infinite velocity. The image we see of a distant planet or galaxy has been carried to us over the course of hundreds of thousands of years. Thus, we are actually looking into the past.

?Mirages? on roads are caused by the scattering of light.

False ? The ?haze? you might see on the highway while driving on a hot day is actually the result of a difference in the density of the air caused by heat. This difference refracts the light and produces a subtle haze.

Objects are closer than they appear in passenger-side mirrors because of the driver?s viewing angle.

False ? The passenger-side mirror is slightly convex to better cover a car?s blind spot. The curvature makes objects appear smaller and therefore farther away.

Fiber-optic cables carry information using light and sound.

False ? Fiber optics, as their name would imply, rely only on light. The cables are actually fine tubes that use the principles of total internal reflection to bounce waves of light along the inside surface ? the result is a cable that can transport information at the speed of light.

Light can be bent, reflected, and refracted.

False ? Light is never actually bent; it can only be reflected and refracted. In refraction, the path of the light changes as it passes from one medium to another; this is commonly referred to as ?bending.?

Reading glasses sometimes appear to have a ?rainbow? on them.

True ? If you orient the surface of a prescription lens just right, you can see a ?rainbow? of color. The resulting rainbow is actually the dispersal of light as it passes through the coating on the surface of the lens.

Polarized sunglasses block out certain wavelengths of light.

False ? Polarized lenses use special dichronic coatings which block out waves with a particular kind of polarization and let through all the rest. The result is that much of the unwanted glare from a light source is removed, but the effect is independent of wavelength.

If there were no atmosphere, there would be no daytime.

True ? Without an atmosphere we would only see light from the sun if we stared directly at it. We have daylight because the Earth?s atmosphere scatters the light across its surface. Scattering lets us see different wavelengths depending on the sun?s position relative to our location.

Compiled by
Steven Spurgeon