The speed of sound in air is about 343 m/s! It varies with temperature (faster in warmer air) and humidity. The speed of sound in water is about 1,480 m/s (about 4.3 times faster than air). In steel, it is about 5,960 m/s (about 17 times faster than air). That is why you see lightning before you hear thunder (light travels much faster than sound). The Mach number is the ratio of speed to the speed of sound. Mach 1 is the speed of sound. Supersonic aircraft (Concorde) fly faster than Mach 1. The sound barrier was first broken by Chuck Yeager in 1947 (Bell X-1). So the speed of sound in air is about 343 m/s.

The cochlea converts vibrations into electrical signals! The ear drum (tympanic membrane) vibrates first. The ossicles (malleus (hammer), incus (anvil), stapes (stirrup)) amplify and transmit vibrations to the oval window, which transfers them to the fluid in the cochlea. The cochlea's hair cells bend, generating nerve impulses. Loud sounds can damage hair cells (permanent hearing loss). Protect your hearing by wearing earplugs at concerts and turning down the volume on headphones. So the cochlea is the answer.

The Doppler effect is the correct answer! The formula for the observed frequency is f' = f (v ± v_o)/(v ∓ v_s). The Doppler effect is used in police radar (measuring speed), weather radar (Doppler radar), and astronomy (redshift indicates distant galaxies are moving away, supporting the Big Bang theory). The change in pitch is noticeable when a race car passes you. So the Doppler effect is the answer.

The speed of light is 300,000 km/s! It takes about 8 minutes and 20 seconds for light to travel from the Sun to Earth. Light travels slower in water, glass, and other media. The refractive index n = c/v. Light is an electromagnetic wave, with a range of wavelengths (visible light, radio, X-rays, etc.). The visible spectrum ranges from about 400 nm (violet) to 700 nm (red). So the speed of light is 300,000 km/s.

Convex mirrors are used for wider views! They reduce blind spots. Concave mirrors (like makeup mirrors) magnify. They can also produce real images (used in telescopes and satellite dishes). Plane mirrors (flat) produce images the same size. The law of reflection applies to all mirrors. So convex mirrors are used in car side-view mirrors.

Refraction is the answer! The refractive index of water is about 1.33, of glass about 1.5, of diamond about 2.4. Lenses (convex and concave) use refraction. A convex lens converges light (magnifying glass, camera, eye). A concave lens diverges light. The lens in your eye focuses light on the retina. Corrective lenses (glasses) compensate for refractive errors (myopia (nearsightedness) and hyperopia (farsightedness)). Mirages are caused by refraction (bending of light due to temperature gradients in air). So refraction causes the straw to appear bent.

Dispersion is the answer! The order of colors is ROYGBIV (red, orange, yellow, green, blue, indigo, violet). Water droplets in the atmosphere act like prisms. A rainbow is always opposite the Sun. The primary rainbow has red on the outside; the secondary rainbow (if visible) has red on the inside. So dispersion splits white light into colors.

Radio waves have the longest wavelength! The order (increasing frequency, decreasing wavelength): radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays. Radio waves (AM, FM, TV, cell phones, Wi-Fi, Bluetooth). Microwaves (microwave ovens, radar, satellite communication). Infrared (remote controls, thermal imaging). Visible light (what we see). Ultraviolet (UV) (sunburns, sterilization). X-rays (medical imaging, security). Gamma rays (nuclear medicine, cancer treatment, astronomy). So radio waves have the longest wavelength.

Cone cells detect color! There are about 6-7 million cones in the human retina. Rods (about 120 million) detect brightness (scotopic vision). Cones are concentrated in the fovea (center of vision). The three types of cones are L-cones (long wavelength, red), M-cones (medium wavelength, green), and S-cones (short wavelength, blue). Color blindness (affects about 8% of males, 0.5% of females) is usually due to a genetic defect in L- or M-cones. So cone cells detect color.

Light travels faster! The speed of light is about 300,000 km/s; the speed of sound is about 0.343 km/s. Light travels about 874,000 times faster than sound. So you see lightning first, then hear thunder. The delay tells you how far away the lightning is (5 seconds = 1 mile). Sound cannot travel in a vacuum (space). Light can travel through a vacuum. Light is an electromagnetic wave; sound is a mechanical wave. So light is faster.