The Physics of Waves: Light Waves, Sound Waves and Ultrasound MCQs

The Physics of Waves: Light Waves, Sound Waves and Ultrasound

The energy carried by a photon of electromagnetic radiation is proportional to its:

Frequency

Speed

Wavelength

Amplitude

When referring to the energy in a photon (a packet) of radiation, the equation E = h × f relates the energy E of a photon to its frequency, f.

Author: rikazzz Comment

The Physics of Waves: Light Waves, Sound Waves and Ultrasound

What is the measure known as “sound level”?

A subjective measure of the perceived loudness of a sound (in dB)

A graph of the levels of sound of different frequencies that we perceive as equal in loudness (in phone)

The frequency of the sound that produces the loudest response in a healthy hearing mechanism (in Hz)

The objectively measured amount of sound energy carried by a sound wave (in W/m²)

Sound level is subjective, in that it is perceived by the hearer and depends on the frequency/ies of the sound. The unit is the decibel.

Author: rikazzz Comment

The Physics of Waves: Light Waves, Sound Waves and Ultrasound

To what radiation does the term “nonionising radiation” refer? To radiation that consists of photons with energy that is:

Not high enough to knock electrons out of atoms but is high enough to produce ions

Sufficient to generate ions in the material that the photons enter

Not sufficient to generate ions in the material that the photons enter

High enough to knock electrons out of atoms but not high enough to pro-duce ions

The term “nonionising” implies that ions are not produced. Ions are produced when one or more electrons are removed from an atom.

Author: rikazzz Comment

The Physics of Waves: Light Waves, Sound Waves and Ultrasound

When a sound with a particular frequency is played at a loudness of 60 dB, and compared to the same sound played at 10 dB, what can be said about the intensity (in W/m²) of the 60 dB sound? It is:

50 times more intense than the 10 dB sound

5000 times more intense than the 10 dB sound

50,000 times more intense than the 10 dB sound

100,000 times more intense than the 10 dB sound

If a sound is 10 times more intense (10 × more W/m²) than another sound of the same frequency, then it is 10 dB (1 B) louder. If it is 100 times more intense, it sounds 20 dB louder. Hence, remembering the logarithmic nature of the loudness scale, a sound that is 50 dB (5 B) louder than another, is also 100,000 times (10⁵) more intense.

Author: rikazzz Comment

The Physics of Waves: Light Waves, Sound Waves and Ultrasound

What can be said about the collimated beam of electromagnetic energy produced by an Nd-YAG laser?

It has a higher frequency than visible light energy.

It stimulates the production of light as it passes through air.

It is produced when electrons change energy levels.

It consists of waves of two or more frequencies.

The EM energy produced by a laser occurs when electrons drop to a lower energy level from their “excited” state. An Nd-YAG laser produces one frequency of near infrared light (which is of lower frequency than visible light).

Author: rikazzz Comment

The Physics of Waves: Light Waves, Sound Waves and Ultrasound

When a Doppler ultrasound device is used to investigate the blood flow in an artery, what happens to the ultrasound when it reflects from a red blood cell?

The frequency of the ultrasound is increased.

The frequency of the ultrasound is changed.

The frequency of the ultrasound is decreased.

The frequency of the ultrasound is unchanged.

When ultrasound reflects from a moving object (e.g. a RBC), its frequency is changed. This is a manifestation of the “Doppler effect”. The frequency will increase if the RBC is travelling towards the ultrasound transducer. The frequency will decrease if the RBC is travelling away from the transducer. As the question does not state the direction of travel of the RBC, one cannot choose either of A or C.

Author: rikazzz Comment

The Physics of Waves: Light Waves, Sound Waves and Ultrasound

Material that is unsuitable for use in a LASER lacks which of the following properties?

A metastable excited state

A short-lived ground state

The ability to spontaneously emit radiation

A long-lived ground state

A metastable excited state – that is, one that persists for longer than an excited state normally exists – is required for lasing action.

Author: rikazzz Comment

The Physics of Waves: Light Waves, Sound Waves and Ultrasound

Ultrasound is least useful for examining what?

Heart

Lungs

Kidneys

Uterus

The lungs contain air which reflect all of the ultrasound reaching it, making the lungs opaque to ultrasound.

Author: rikazzz Comment

The Physics of Waves: Light Waves, Sound Waves and Ultrasound

Consider the situation where a light wave travelling in air strikes a glass surface with an angle of incidence of 20°. Which of the following statements is true?

The angle formed by the incident ray and the normal will be 20°.

The angle of refraction will be greater than 20°.

The angle formed by the incident ray and the glass surface is 20°.

There will be no refracted ray. That is, total internal reflection will occur.

The “angle of incidence” is defined as angle formed by the incident ray and a line perpendicular with the surface (i.e. the “normal”). Total internal reflection may occur when light passes from glass to air, not air to glass.

Author: rikazzz Comment

The Physics of Waves: Light Waves, Sound Waves and Ultrasound

The change in pitch (frequency) of a sound when there is relative motion between the sound source and the human observer is known as the:

Resonance effect

Interference effect

Diffraction effect

Doppler effect

This change of frequency effect is apparent when listening to the sound of a motor vehicle engine as it approaches you and then as it continues past you.

Author: rikazzz Comment