EM Waves

Question 1

What are electromagnetic (EM) waves classified as?

Answer 1

Transverse waves

EM waves are transverse waves, meaning their oscillations are perpendicular to the direction of wave propagation.

Question 2

Do all EM waves travel at the same speed in a vacuum?

Answer 2

Yes

All EM waves travel at the speed of light in a vacuum, approximately 3 x 10^8 m/s.

Question 3

What causes refraction of EM waves?

Answer 3

Different speeds in different materials

Refraction occurs because EM waves travel at different speeds when passing through various materials.

Question 4

What is the wavelength range of EM waves?

Answer 4

From around 10^-15 m to more than 10^4 m.

Question 5

How are EM waves grouped?

Answer 5

Based on their wavelength and frequency

There are seven basic types of EM waves that merge to form a continuous spectrum.

Question 6

What generates EM waves?

Answer 6

Changes in atoms and their nuclei

For example, gamma rays are produced by changes in the nucleus, while visible light results from changes in an electron’s energy level.

Question 7

Which part of the EM spectrum can human eyes detect?

Answer 7

Visible light.

Question 8

List the colors of visible light from longest to shortest wavelength.

Answer 8

• Red
• Orange
• Yellow
• Green
• Blue
• Indigo
• Violet

Question 9

What type of energy do all EM waves transfer?

Answer 9

Energy from a source to an absorber

For example, infrared waves transfer energy from an electric heater to a person.

Question 10

How does the frequency of an EM wave relate to its energy transfer?

Answer 10

Higher frequency means more energy transfer.

Question 11

What happens to EM waves at a boundary between different materials?

Answer 11

They can be absorbed, transmitted, refracted, or reflected.

Question 12

True or False: Radio waves can be absorbed by the body.

Answer 12

False

Radio waves are transmitted through the body without being absorbed.

Question 13

What is a potential danger of microwaves?

Answer 13

They can cause heating of cells.

Question 14

What is ultraviolet (UV) radiation classified as?

Answer 14

Ionizing radiation.

Question 15

What type of damage can UV radiation cause?

Answer 15

• Skin cancer
• Eye damage
• Other eye conditions

Question 16

How do X-rays and gamma rays affect biological tissues?

Answer 16

They can cause mutations and damage cells.

Question 17

What mnemonic can help remember the order of EM waves?

Answer 17

‘Rock Music Is Very Useful for Ynerimento with Goats’.

Question 18

What creates radio waves?

Answer 18

Oscillating electric and magnetic fields

These are produced by oscillating charges in alternating currents.

Question 19

What is the role of a transmitter in radio waves?

Answer 19

It creates radio waves by oscillating charges.

Question 20

What happens when radio waves reach a receiver?

Answer 20

They are absorbed and cause electrons to oscillate.

Question 21

What type of radio waves can be received halfway around the world?

Answer 21

Long-wave radio (1 - 10 km).

Question 22

Why can short-wave radio signals be received at long distances?

Answer 22

They are reflected by the Earth’s atmosphere.

Question 23

What technology uses short-wave radio waves for data transmission?

Answer 23

Bluetooth.

Question 24

What is necessary for receiving TV and FM radio transmissions?

Answer 24

Direct sight of the transmitter.

Question 25

What type of EM waves are used for communication with satellites?

Answer 25

Microwaves and relatively high frequency radio waves.

Question 26

How does a satellite transmit signals back to Earth?

Answer 26

It receives a signal and transmits it back in a different direction.

Question 27

What do microwaves do in microwave ovens?

Answer 27

Microwaves are absorbed by water molecules in food, causing them to heat up and cook the food quickly. ## Footnote Microwaves penetrate up to a few centimeters into the food before being absorbed.

Question 28

How does infrared radiation relate to temperature?

Answer 28

Infrared radiation is emitted by all hot objects; hotter objects emit more IR radiation. ## Footnote Infrared cameras detect IR radiation and convert it into an electrical signal for thermal imaging.

Question 29

What is thermal imaging?

Answer 29

Thermal imaging is the display of infrared radiation detected by cameras as a picture. ## Footnote Different colors represent different amounts of infrared radiation detected.

Question 30

What happens when infrared radiation is absorbed by objects?

Answer 30

Objects get hotter as they absorb infrared radiation. ## Footnote This principle is used in cooking food and heating rooms with electric heaters.

Question 31

How can infrared radiation be used for communication?

Answer 31

Infrared radiation can transfer information, such as sending files between devices or controlling TVs with remote controls. ## Footnote The devices must be in line of sight, and the distance must be relatively short.

Question 32

What is the role of optical fibers?

Answer 32

Optical fibers carry data over long distances as pulses of infrared radiation using total internal reflection. ## Footnote They usually employ a simple wavelength to prevent dispersion.

Question 33

What is visible light used for?

Answer 33

Visible light is used for illumination and photography. ## Footnote Photographic film reacts to light to create images.

Question 34

How do digital cameras work?

Answer 34

Digital cameras use image sensors to detect visible light and generate an electrical signal that is converted into a digital image. ## Footnote This image can be stored digitally or printed.

Question 35

What is fluorescence?

Answer 35

Fluorescence is when ultraviolet radiation is absorbed and visible light is emitted. ## Footnote This property is utilized in fluorescent lamps and security pens.

Question 36

How do fluorescent lamps operate?

Answer 36

Fluorescent lamps use ultraviolet radiation to emit visible light and are energy-efficient. ## Footnote They are suitable for long-term lighting needs.

Question 37

What is a use of ultraviolet radiation in security?

Answer 37

Ultraviolet radiation is used to mark property with invisible ink that glows under UV light. ## Footnote This helps identify stolen property.

Question 38

What is one application of UV radiation in sterilization?

Answer 38

Ultraviolet radiation is used to sterilize water by killing bacteria. ## Footnote Gamma rays can also be used for similar sterilization purposes.

Question 39

What are X-rays used for?

Answer 39

X-rays are used to view the internal structure of objects and materials, including the human body. ## Footnote They are essential for diagnosing broken bones in medical settings.

Question 40

How do X-ray images form?

Answer 40

X-ray images are formed by directing X-ray radiation through an object onto a detector plate, producing a negative image. ## Footnote The denser materials absorb more X-rays, appearing brighter.

Question 41

What is the use of gamma rays in medicine?

Answer 41

Gamma rays are used to sterilize medical instruments and in cancer treatments. ## Footnote They target cancer cells while minimizing damage to healthy cells.

Question 42

True or False: Gamma rays can be used to kill microbes in food.

Answer 42

True ## Footnote This method keeps food fresh without freezing or cooking.