The Electromagnetic Spectrum

radio broadcasts

Microwaves are used for all of the following except a. radar systems b. cooking food c. radio broadcasts d. cellular phones

detect objects and measure their speed

Radar is a system that uses reflected radio waves to

microwaves

Radar uses ______________ to tell the position or speed of objects.

different wavelengths of light refract by different amounts

When white light passes through a prism, a rainbow is formed because

Red light has the longest wavelength and violet light has the shortest wavelength.

Which color of light has the longest wavelength? The shortest wavelength?

Fluorescent light bulbs give off very little energy as infrared rays.

Which light bulbs give off very little energy as infrared ways?

infrared rays

Which of the following can be sensed by humans? a. x-rays b. ultraviolet rays c. radar d. infrared rays

incandescent lights

Which of the following uses a filament to produce light? a. incandescent lights b. vapor lights c. fluorescent lights d. neon lights

Wave A is an AM wave (only its amplitude varies). Wave B is an FM wave (only its frequency varies).

Which wave shown below is an AM wave? Which is an FM wave? Explain your answers. (see pg. 606 in textbook)

No, to use the direct path, the signal would have to pass through Earth. This couldn't happen because the signal would be blocked by Earth and not reach the house.

Would it be a better idea to send signals in the direct path from transmitting tower to the house on the other side of Earth rather than the long way using a satellite? Explain.

travel at the speed of sound

Electromagnetic waves

Infrared waves have higher frequencies, and therefore more energy than radio waves.

Explain why the energy of infrared rays is greater than the energy of radio waves.

amplitude modulation

In ________________, the amplitude of a wave is changed.

frequencies

All electromagnetic waves travel at the same speed through the same medium, but they have different wavelengths and

thermogram

An infrared camera takes a picture called a(n)

In both, sound waves are transformed to radio signals. In the method pictured, the signal is relayed using a satellite. A cellular phone system relays the radio signal through one or several cells to a hub with receivers and transmitters before it reaches its destination.

Compare and contrast this use of satellites to send a telephone message with making a local phone call using a cellular phone. (see pic on study guide)

luminous

A(n) _____________ object gives of its own light.

8 minutes

About how fast does it take light from the sun to reach Earth?

electrical and magnetic energy

Electromagnetic waves are transverse waves that transfer

visible light

Electromagnetic waves that you can see are called _____________.

FM radio signals don't travel very far as 2 radio stations that are far enough apart can operate on the same frequency without interference.

How can 2 FM radio stations in the US have the same frequency without interfering with each other?

Because sunlight travels to the Earth through the vacuum of space; Because radio waves travel back and forth through Earth and satellites in space.

How do you know that electromagnetic waves can travel through a vacuum?

1. X-rays are used to form images to diagnose broken bones. 2. Gamma rays are used to treat cancer.

Identify 2 ways electromagnetic radiation is used in medicine.

90 degrees

If 2 polarizing filters are placed so that one is rotated ________ relative to the other, no light can pass through.

heat or infrared waves

Most of the energy produced by an incandescent light bulb is given off as

killing bacteria

One application of ultraviolet rays is

incandescent light

A light bulb that glows with a filament inside it gets hot is a(n)

halogen light

A ________________ contains a filament and a gas such as iodine or bromine.

transmits signals using high-frequency microwaves

A cellular phone

photoelectric effect

In the ______________, light strikes a material and causes electrons to be ejected.

Visible light, should go between infrared and ultraviolet rays.

In the electromagnetic spectrum shown on the study guide, one kind of electromagnetic wave is missing. Which kind of electromagnetic wave is missing, and where does it belong in the spectrum?

polarized light

Light that vibrates in only one direction is called

A FM station would go to the right of the arrow pointing to the AM station. FM frequencies are higher than AM. The electromagnetic spectrum is arranged with low frequencies to the left and high to the right.

The arrow points to the frequency of an AM radio station. Would a pointer to an FM station be to the right of the left of that arrow? Explain how you know. (see pic on study guide)

radio waves

The electromagnetic waves with the longest wavelengths and lowest frequencies are

fluorescent

The type of light in which a powder gives off visible light is a(n) _________________ light.

radio station transmitters

To send a television signal across the country, a television network can use

Light sometimes acts as a wave

What can the use of a polarizing filter indicate about light?

frequency

When a AM radio station broadcasts, the ______________ of the wave remains constant.

frequency

When an FM radio station broadcasts, the ______________ of the wave varies.