WAVE TYPES AND CHARACTERISTICS

Adapted from TEA 10th grade Science Study Guide

What are the types of waves and how do they travel?

A wave is a disturbance that transfers energy from one place to another. All waves are produced by some kind of vibration. In a transverse wave the vibration is perpendicular to the direction in which the wave travels. For example, if a transverse wave travels from left to right, the medium vibrates up and down.

TYPES OF WAVES

In a longitudinal wave the vibration of the wave is parallel to the direction in which the wave travels. If a longitudinal wave travels from left to right, the medium vibrates left and right as well.

Remember! A medium such as air or water is the material or matter through which a wave travels.

How do scientists measure waves?

Scientists measure waves by describing their properties. Some of the properties of waves are wavelength, amplitude, speed, and frequency. Take a look at the transverse wave below. The wavelength is the distance from one crest (or high point) to the next or from one trough (or low point) to the next. Because wavelength is a distance, it can be measured in meters (m).

Wave PropertiesThe amplitude of the wave is the distance from the resting

position to a crest or from the resting position to a trough. Amplitude can also be measured in meters.

The greater the amplitude of a wave, the more energy the wave transfers. If you think about it, this makes sense. A huge ocean wave has a much larger amplitude than a tiny ripple. It also has more energy. A tiny ripple doesn’t have enough energy to knock you off a surfboard, but a huge ocean wave might!

What is the difference between speed and frequency?

To measure frequency, you need to figure out how many wavelengths pass a particular point in one unit of time. Frequency is measured in units called hertz (Hz). One hertz is equal to 1 wave per second. For example, if 3 complete wavelengths pass you every second, the frequency is 3 waves per second or 3 hertz.

The speed of a wave is the distance the wave travels in one unit of time. So the speed of a wave can be measured in units of meters per second (m/s).

What about electromagnetic waves? What are they?

Electromagnetic waves include radio waves, microwaves, infrared waves, visible light, ultraviolet rays, and X rays. Without electromagnetic waves, you wouldn’t be able to listen to the radio, watch television, use a microwave oven, or even look at a sunset.

Electromagnetic waves are different from other waves because they can travel through a vacuum like space. They don’t require a medium as other waves do.

All electromagnetic waves travel through a vacuum at the same speed. This constant speed is often called the speed of light. The speed of light is equal to 3×108 meters per second.

Wait a minute. Isn’t there a formula about waves on the formula chart? How do I use it?

The formula chart tells you that the velocity of a wave equals its frequency times its wavelength. Suppose a radio station broadcasts radio waves at a frequency of 1.021 ×108 hertz. Let’s find the wavelength of the waves.

We already know which formula we want to use—the one that relates frequency to wavelength.

Velocity of a wave = frequency × wavelength

fv

Let’s rearrange this formula so that we can solve for wavelength. Divide both sides of the equation by frequency.

wavelengthfrequency

f a wavevelocity o

f

v

But we don’t know the velocity of the wave. How can we solve for the wavelength without the velocity?

Remember! Radio waves are electromagnetic waves, and travel at the speed of light.

The constants/conversions chart tells us that the speed of light is 3 × 108 m/s. Now we can substitute the values we know into the formula and solve for wavelength.

sm

sm

/10021.1

/1038

8

f

v

m 938.2

frequency

f a wavevelocity owavelength

Sample Problems cont.

Electrical Energy - Moving electrons in a path is

electricity• Electrical Potential Difference (V) is measured in Volts • Electric Current (I) is the rate of moving electric charges

and is measured in Amperes • Resistance or opposition to the movement of the energy is

called Resistance (R). Measured in Ohms (Ω)

Formula From Chart:

I= V/R or

V = I R

Circuits – 2 types

• Series circuits are the most simple.

• One (1) path for the current to travel.

• Contains an energy source, a path, and a load (something for it to do, like a lamp)

Circuits – 2 types• Parallel circuits

provide more than one path for the current to travel.

• Most circuits are parallel, since if one lamp goes out, the others can stay lit.

F. QG. RH. SJ. T

6. Which switches, if opened, will cause the light bulb to stop

glowing?

It is the only switch in series to both the battery and light.

USE THE FORMULA SHEET!!

• What is the current in a copper wire that has a resistance of 2 ohms and is connected to a 9 volt electrical source?A. 0.22 ampB. 4.5 ampsC. 11.0 ampsD. 18.0 amps

V = I R so,

9V = I x 2 ohms or 4.5 amps

Remember• Use your Equation Sheet

• Use your Calculator

• Use your Periodic Table