Chapter 1: Light and Waves

What is the formula for calculating the wavelength of a wave?

What is the speed of light in a vacuum, c?

• 300,000 km/s

• 150,000 km/s

• 500,000 km/s

• 100,000 km/s

Answer explanation

The speed of light in a vacuum, denoted as c, is universally accepted to be approximately 300,000 km/s. This is the fastest speed at which information or matter can travel.

What is the difference between a transverse and a longitudinal wave?

• Transverse waves vibrate particles parallel to the direction of travel, while longitudinal waves vibrate particles perpendicular to the direction of travel.

• Transverse waves vibrate particles perpendicular to the direction of travel, while longitudinal waves vibrate particles parallel to the direction of travel.

• Both transverse and longitudinal waves vibrate particles perpendicular to the direction of travel.

• Both transverse and longitudinal waves vibrate particles parallel to the direction of travel.

Answer explanation

Transverse waves vibrate particles perpendicular to the direction of travel, such as in water waves, while longitudinal waves, like sound waves, vibrate particles parallel to the direction of travel. This distinction is key.

What is the difference between a mechanical and a non-mechanical wave?

• Mechanical waves do not require a medium, while non-mechanical waves do.

• Mechanical waves require a medium, while non-mechanical waves do not.

• Both mechanical and non-mechanical waves require a medium.

• Neither mechanical nor non-mechanical waves require a medium.

Answer explanation

Mechanical waves, like sound waves, require a medium (solid, liquid, or gas) to travel through, while non-mechanical waves, such as light waves, can propagate through a vacuum. Thus, the correct choice is that mechanical waves require a medium.

How does a mechanical wave motion transfer energy from one place to another?

• By transferring matter along with energy.

• By transferring energy without transferring matter.

• By transferring both energy and matter.

• By transferring neither energy nor matter.

Answer explanation

Mechanical waves transfer energy through vibrations in a medium, but the medium itself does not move with the wave. Thus, energy is transferred without transferring matter, making the correct choice: 'By transferring energy without transferring matter.'

What is the measure of the size of wave vibrations called?

• Frequency

• Wavelength

• Amplitude

• Speed

Answer explanation

The measure of the size of wave vibrations is called amplitude. It represents the maximum displacement of points on a wave, indicating how strong or intense the wave is.

With what units is frequency of a wave measured?

• Metres (m)

• Seconds (s)

• Hertz (Hz)

• Metres per second (m s⁻¹)

Answer explanation

Frequency of a wave is measured in Hertz (Hz), which indicates the number of cycles per second. Other options like metres or seconds do not represent frequency, making Hertz the correct choice.

What does the symbol λ represent in wave equations?

• Speed of the wave

• Frequency of the wave

• Wavelength of the wave

• Period of the wave

Answer explanation

In wave equations, the symbol λ (lambda) represents the wavelength of the wave, which is the distance between successive crests or troughs. This distinguishes it from speed, frequency, and period.

Define the amplitude of a transverse wave in a slinky spring.

• The maximum displacement from the rest position

• The speed of the wave

• The frequency of the wave

• The wavelength of the wave

Answer explanation

The amplitude of a transverse wave is defined as the maximum displacement from the rest position. This means it measures how far the wave moves from its equilibrium position, making it the correct choice.

Which of the following is equal to the period, T, of a wave?

• T = 1/f

• T = f/λ

• T = v/λ

• T = λ/v

Answer explanation

The period, T, of a wave is the reciprocal of frequency, f. Therefore, T = 1/f is the correct relationship. The other options relate to wave speed and wavelength, but do not define the period.