Electromagnetic Waves Unit

Which of the following statements about electromagnetic waves is true?

• Vibrating charged particles generate electric fields.

• Electromagnetic waves can travel only through matter.

• Electromagnetic waves form when an electric charge accelerates.

• All of the above

Answer explanation

Electromagnetic waves are a type of wave that consist of oscillating electric and magnetic fields that travel through space. These waves are produced by the acceleration of charged particles, which creates a changing electric field that generates a changing magnetic field and vice versa, forming a self-sustaining wave.

Option A is partially correct in that vibrating charged particles do generate electric fields, but this is not specific to electromagnetic waves.

Option B is false as electromagnetic waves can travel through a vacuum, meaning they do not require matter to propagate.

What does a wave carry?

• data

• energy

• matter

• water

Answer explanation

A wave carries energy from one place to another. The energy can be in the form of sound, light, or other forms of electromagnetic radiation. The wave carries the energy through the medium it is traveling through, such as air, water, or a solid material. The energy is transferred from one point to another as the wave moves.

In the case of electromagnetic waves, such as light or radio waves, the wave carries energy in the form of oscillating electric and magnetic fields, which can interact with matter and produce a variety of effects, such as heating or radiation.

What part of the wave is shown at letter A?

• crest

• wavelength

• trough

• amplitude

Answer explanation

A transverse wave is a type of wave in which the disturbance or oscillation is perpendicular to the direction of wave propagation. The parts of a transverse wave include:

Crest: the highest point of the wave above the equilibrium or rest position

Trough: the lowest point of the wave below the equilibrium or rest position

Amplitude: the distance from the equilibrium position to the crest or trough of the wave, which is a measure of the wave's energy

Wavelength: the distance between two successive crests or troughs of the wave, which is a measure of the length of the wave

Period: the time it takes for one complete cycle of the wave, which is related to the frequency of the wave

Frequency: the number of cycles of the wave per unit time, which is related to the period of the wave

The full range of frequencies of electromagnetic radiation is called

• visible light

• the electromagnetic spectrum

• radio waves

• invisible radiation

Answer explanation

the electromagnetic spectrum. The electromagnetic spectrum is composed of a wide range of frequencies, ranging from radio waves to gamma rays. Each type of electromagnetic radiation has its own unique properties, such as frequency, wavelength, and energy. Radio waves have the longest wavelengths and the lowest frequencies, while gamma rays have the shortest wavelengths and the highest frequencies. The different types of electromagnetic radiation are used for a variety of purposes, such as communication, medical imaging, and astronomy.

Which of the following occurs when electromagnetic waves pass from space to matter?

• It speeds up

• It slows down

• It changes frequency

• It changes wavelength

Answer explanation

When electromagnetic waves pass from space to matter, they slow down.

This phenomenon is called refraction and is due to the change in the speed of light as it passes through different mediums. Electromagnetic waves travel through space at the speed of light, which is approximately 299,792,458 meters per second. However, when they encounter matter, such as air, water, or glass, they slow down due to interactions with the atoms and molecules in the material.

Which shows the correct order from lowest to highest energy for different electromagnetic waves? 

• Light - X-ray - Microwave 

• Gamma ray - Light - Radio wave 

• X-ray - Microwave - Ultraviolet wave  

• Radio wave - Microwave - Gamma ray

Answer explanation

The higher the frequency, the higher the energy.

The electromagnetic spectrum, which is a range of all types of electromagnetic radiation, is arranged from lowest frequency to highest frequency.

Radio waves

Microwaves

Infrared rays

Visible Light

Ultraviolet rays

X-rays

Gamma rays

These also follow a longest to shortest wavelength arrangement.

Which of the following causes a chemical to glow in a fluorescent lightbulb?

• gamma rays

• infrared rays

• radio waves

• ultraviolet rays

Answer explanation

A fluorescent lightbulb contains a gas that emits ultraviolet (UV) radiation when an electric current passes through it. This UV radiation is absorbed by a phosphorescent coating on the inside of the bulb, which causes the coating to emit visible light. The visible light emitted by the phosphorescent coating is what produces the light from a fluorescent bulb.

Which of the following is arranged from least to greatest frequency?

• green, blue, yellow, orange

• red, yellow, blue, violet

• orange, yellow, blue, green

• violet, blue, yellow, red

Answer explanation

Visible light is further divided into the different colors. These are arranged from longest to shortest wavelength, or lowest to highest frequency.

Red

Orange

Yellow

Green

Blue

Violet

In fact, the prefix "infra" means below, that's why the infrared region is the region with the lower frequency/ lower energy from the visible light region. (literally, below red)

Also, the prefix "ultra" means beyond, that's why the ultraviolet region is the region with the higher frequency/ higher energy than the visible light region. (literally, higher than violet)

Which of the following is the same for all electromagnetic waves?

• energy

• frequency

• speed

• wavelength

Answer explanation

All electromagnetic waves, regardless of their frequency or wavelength, travel at the same speed in a vacuum, which is approximately 299,792,458 meters per second, commonly referred to as the speed of light.

Which of the following electromagnetic waves causes sunburns?

• microwaves

• radiowaves

• ultraviolet rays

• x-rays

Answer explanation

Ultraviolet (UV) rays are a type of electromagnetic wave with a higher frequency and energy than visible light but lower energy than X-rays. The UV radiation from the sun is the main cause of sunburns, as it can penetrate the skin and damage the DNA in skin cells. Prolonged exposure to UV radiation can also increase the risk of skin cancer.