# 07.17.2019: Science Notebook Ch. 15

Today’s soundtrack is Stormental: Stormental, a prog metal album with some power metal influence.

I’m reading Chapter 15 of Everything You Need to Ace Science in One Big Fat Notebook, “Light and Sound Waves.”

Light and sound are both carried through waves that oscillate (curve back and forth repeatedly). Mechanical waves can transmit energy through matter; electromagnetic waves carry energy through a vacuum. Sound relies on mechanical waves; for this reason, nobody in space can hear you scream. Light can be carried by either electromagnetic waves or mechanical waves; thus, a beam of light can carry through space or underwater.

There are four properties of a wave:

1. Amplitude (the distance between the wave’s central axis and its peak)
2. Wavelength (the distance that it takes for the wave to repeat itself)
3. Frequency (the number of waves that occur per second, measured in hertz)
4. Wave speed (the time that it takes a wave to move from its origin to a given destination)

There are several factors that influence a wave’s behaviour:

1. Different mediums
1. Mechanical waves travel more quickly through water than air
2. Electromagnetic waves travel more quickly through air than they do water.
2. Reflection
1. Waves can bounce off surfaces: think of an echo or a mirror.
2. The originating wave is called an incident ray; the reflected wave is called a reflected ray.
3. The law of reflection tells us that “a wave reflects at the same angle as the angle that it moved toward the barrier” (p. 147).
3. Refraction
1. The bending of waves as they pass through different mediums: think of putting your hand into an aquarium.
4. Diffraction
1. The bending of waves when a large wave passes through a small hole in a barrier
5. Interference
1. When waves collide with each other, one of two possible outcomes occurs:
1. If they form one large wave, we call it constructive interference
2. If the two waves cancel each other out, we call it destructive interference
6. Absorption
1. Certain substances or mediums may absorb a wave: think about shining a flashlight straight down in the middle of the ocean. The beam likely doesn’t reach the bottom; it gets absorbed by the water.

Electromagnetic waves are made of two parts: an electric field and a magnetic field. These oscillate “at 90-degree angles to each other” (p. 150). We can only see one kind of electromagnetic wave: visible light. There are many kinds of electromagnetic waves: radio waves, microwaves, infrared light, visible light, ultraviolet waves, x-rays, and gamma rays.

Visible light looks white, but it is actually a collection of all colours combined. We can break apart the light into its parts with a prism, and we can see this phenomenon in nature when we look at a rainbow.

Sound is made of just one part: vibrating molecules. This is why sound doesn’t carry in space: there’s no matter for it to transfer through! Sound is easily absorbed over distance, because the molecules shake less and less the further they go. The longer the wavelength of a sound wave, the deeper its pitch. The longer a wavelength is, the deeper its pitch, and the further it carries before being absorbed.

Summary:

1. The mnemonic for the order of colors in the visible spectrum is “ROY G. BIV;” the order of the colors is Red, Orange, Yellow, Green, Blue, Indigo, Violet.
2. A high-intensity sound wave has a large amplitude.
3. Between vapor, liquids, and solids, sound waves travel fasted in solids.
4. The kind of waves that we use to warm up food is microwaves.
5. Gamma rays are harmful high-energy electromagnetic waves.
6. UV rays cause sunburn.
7. Visible light waves are the electromagnetic waves that awe can see.
8. Warm bodies emit infrared waves.
9. A cell phone would not make a sound in space because sound does not carry in a vacuum.
10. Higher-pitched sounds have higher frequencies because their wavelengths are shorter, making them vibrate more times per second.