3. Waves

Question 1

What is a wave?

Answer 1

A wave is a disturbance caused by an oscillating source that transfers energy and information in the direction of wave travel without transferring matter.

Question 2

What are transverse waves?

Answer 2

Transverse waves are waves where the oscillations are perpendicular to the direction of energy transfer.

Question 3

Define longitudinal waves.

Answer 3

Longitudinal waves are waves where the oscillations are parallel to the direction of energy transfer, with areas of compression and rarefaction.

Question 4

What are electromagnetic waves?

Answer 4

Electromagnetic waves are transverse waves that transfer energy from the source of the waves to an absorber.

Question 5

What is the speed of electromagnetic waves through a vacuum?

Answer 5

All types of electromagnetic waves travel at the same speed through a vacuum, which is approximately 3.00 × 10^8 meters per second, commonly represented as “c.”

Question 6

What part of the electromagnetic spectrum is visible to the human eye?

Answer 6

Visible light is the part of the electromagnetic spectrum detected by human eyes.

Question 7

What is the order of electromagnetic waves within the spectrum, based on energy?

Answer 7

The order of electromagnetic waves within the spectrum, based on increasing energy, is:
radio waves
microwaves
infrared radiation
visible light
ultraviolet radiation
X-rays
gamma rays.

Question 8

What is the range of wavelengths for electromagnetic waves in the spectrum?

Answer 8

The wavelengths of electromagnetic waves range from about 10^-15 meters (gamma rays) to 10^4 meters and beyond (radio waves).

Question 9

How are infrared waves used in practical applications?

Answer 9

Infrared waves are used in various practical applications, such as TV remote controls, night vision devices, heating systems, and thermal imaging cameras.

Question 10

What are some hazards associated with exposure to electromagnetic waves?

Answer 10

Excessive exposure to electromagnetic waves can be hazardous.
Low-energy waves like microwaves and infrared waves can cause heating effects, while higher-energy waves like ultraviolet, X-rays, and gamma rays can cause ionization, leading to various health risks such as skin burns, cancer, and genetic mutations.

Question 11

What are sound waves?

Answer 11

Sound waves are longitudinal waves that cause vibrations in a medium, which are detected as sound.

Question 12

What is ultrasound?

Answer 12

Ultrasound is acoustic energy in the form of waves with a frequency higher than the upper limit of hearing for humans. (20,000 Hz)

Question 13

How are ultrasound waves used in medicine?

Answer 13

Ultrasound waves are used in medicine for prenatal scanning and the removal of kidney stones.

Question 14

What are some properties of X-rays?

Answer 14

Properties of X-rays include:
- They affect a photographic film in the same way as light.
- They are absorbed strongly by metal and bone.
- They are transmitted by healthy tissue.

Question 15

What are some characteristics of X-rays?

Answer 15

X-rays are part of the electromagnetic spectrum.
They have a very short wavelength, high energy, and can cause ionization.

Question 16

How are X-rays utilized in medicine?

Answer 16

X-rays can be used to diagnose medical conditions such as bone fractures, dental problems, and in computed tomography (CT) scanning. Additionally, X-rays are employed in treating certain conditions like killing cancer cells through radiation therapy.

Question 17

Why is it necessary to take precautions when working with high-energy ionizing radiation?

Answer 17

Precautions are necessary because high-energy ionizing radiation can be hazardous to health. It’s important to monitor and minimize exposure levels to ensure the safety of individuals working with such radiation.

Question 18

What are some behaviors of sound waves?

Answer 18

Sound waves can be reflected, creating echoes, and diffracted, which allows them to bend around obstacles.

Question 19

How are ultrasound waves utilized in distance measurement?

Answer 19

Ultrasound waves are partially reflected when they encounter a boundary between two different media. The time taken for these reflections to reach a detector can be used to determine the distance to the boundary.

Question 20

What is the principle behind reflection of waves?

Answer 20

When waves are reflected, the angle of incidence is equal to the angle of reflection.

Question 21

Explain the concept of the normal in the context of wave reflection.

Answer 21

In wave reflection, the normal is a construction line perpendicular to the reflecting surface at the point of incidence.

Question 22

Describe the characteristics of the image produced by a plane mirror.

Answer 22

The image produced in a plane mirror is virtual, upright, and laterally inverted.

Question 23

What is refraction, and how does it occur in waves?

Answer 23

Refraction is the bending of waves as they pass from one medium to another with a different density. It occurs due to the change in wave speed.

Question 24

Explain how light waves are refracted at an interface.

Answer 24

When light enters a denser medium, it is refracted towards the normal.

Conversely, when light enters a less dense medium, it is refracted away from the normal.

Question 25

What is total internal reflection, and when does it occur?

Answer 25

Total internal reflection is a special case of refraction that occurs when the angle of incidence within the denser medium is greater than the critical angle.

Question 26

How can optical fibers transmit light through total internal reflection?

Answer 26

Optical fibers can transmit light through total internal reflection by confining light within the fiber and allowing it to bounce off the walls due to the phenomenon of total internal reflection.

Question 27

What is a lens, and how does it form an image?

Answer 27

A lens is an optical device that forms an image by refracting light.

In a convex (converging) lens, parallel rays of light are brought to a focus at the principal focus.

In a concave (diverging) lens, parallel rays of light diverge as if coming from the principal focus.

Question 28

How is the focal length of a lens defined?

Answer 28

The focal length of a lens is the distance from the lens to the principal focus.

Question 29

What factors determine the nature of an image formed by a lens?

Answer 29

The nature of an image formed by a lens is determined by its size relative to the object, whether it is upright or inverted relative to the object, and whether it is real or virtual.

Question 30

How do you calculate magnification?

Answer 30

magnification = image height / object height

Question 31

What are the structures of the eye?

Answer 31

• retina
• variable focus lens
• cornea
• pupil/iris
• ciliary muscle
• suspensory ligaments

Question 32

How can lenses correct long sight?

Answer 32

Long sight, caused by the eyeball being too short or the eye lens being unable to focus a sharp image on the retina.

It can be corrected using converging lenses to converge light rays onto the retina.

Question 33

How can lenses correct short sight?

Answer 33

Short sight, caused by the eyeball being too long or the eye lens being unable to focus a sharp image on the retina.

It can be corrected using diverging lenses to diverge light rays before they enter the eye, allowing them to focus properly on the retina.

Question 34

What are lasers primarily used for, and where can they be employed in the medical field?

Answer 34

Lasers are concentrated sources of light primarily used for cutting, cauterizing, and burning.

In the medical field, lasers can be used in eye surgery to correct visual defects.

Question 35

How can the structure and function of the eye be compared to that of a camera?

Answer 35

In the eye, the image is brought to focus on the retina by changing the shape of the lens. Similarly, in a camera, the image is brought to focus on the film or CCD sensor by varying the distance between the film and the lens.

The film (or CCD sensor) in a camera is equivalent to the retina in the eye.

Question 36

What happens to parallel rays of light in a convex (converging) lens?

Answer 36

Parallel rays of light are brought to a focus at the principal focus of the convex lens.

Question 37

How do parallel rays of light behave in a concave (diverging) lens?

Answer 37

Parallel rays of light diverge as if coming from the principal focus of the concave lens.

Question 38

What is the focal length?

Answer 38

The distance from the lens to the principal focus is called the focal length

Question 39

What defines the nature of an image formed by a lens or mirror?

Answer 39

The nature of an image is determined by three factors:
- its size relative to the object,
- whether it is upright or inverted relative to the object,
- whether it is real or virtual.