unit 2 radio physics quiz

In intraoral radiology, which tube voltage (kVp) balances image quality and dose?

A) 40–50 kVp

B) 60–70 kVp

C) 80–90 kVp

D) 100–120 kVp

60–70 kVp

What happens to the intensity of the X-ray beam as it penetrates tissue?

A) It progressively decreases due to absorption and scattering (attenuation).
B) It completely converts into visible light upon impact.
C) It increases as photons multiply.
D) It remains constant regardless of thickness.

A) It progressively decreases due to absorption and scattering (attenuation).

Which type of collimation is recommended to minimize the irradiated field?

A) Divergent conical collimator.
B) Wide circular collimation.
C) Without any collimator.
D) Rectangular collimation.

D) Rectangular collimation.

What does the radiation protection principle ALARA stand for?

A) Always Low And Radiation Approved.
B) As Low As Reasonably Achievable.
C) As Long As Radiation Absorbs.
D) Absolute Limit Against Radiation Accidents.

B) As Low As Reasonably Achievable.

What happens when filtering a polychromatic beam ("beam hardening")?

A) The proportion of low-energy photons increases.
B) The beam automatically converts into gamma rays.
C) Low-energy photons are removed, increasing the mean energy of the beam.
D) Beam quality decreases for diagnosis.

C) Low-energy photons are removed, increasing the mean energy of the beam.

How do charged particles lose energy when passing through matter?

A) Converted solely into mass.

B) Through spontaneous thermal evaporation.

C) Through electromagnetic interactions with electrons and nuclei.

D) Solely by bouncing in a vacuum.

C) Through electromagnetic interactions with electrons and nuclei.

To avoid scattered radiation, where should the operator stand?

A) In the direct path of the primary beam.

B) Directly in front of the patient at 180°.

C) At 45° to the beam without keeping distance.

D) Between 90° and 135° relative to the primary beam axis.

D) Between 90° and 135° relative to the primary beam axis.

Why do photons NOT undergo braking radiation (bremsstrahlung)?

A) Because they have too high a mass.
B) Because they only interact with air.
C) Because they always travel at the speed of sound.
D) Because they lack electric charge and mass

D) Because they lack electric charge and mass.

How do thickness and density affect X-ray attenuation?

A) Greater thickness and density result in greater attenuation.
B) Dense tissues accelerate photons.
C) Greater thickness results in lower attenuation.
D) Density does not affect attenuation.

A) Greater thickness and density result in greater attenuation.

Which principle complements ALARA by optimizing the dose to the patient and indication?

A) Always repeat radiographs.
B) Mandatory non-use of aluminum filters.
C) As Low As Diagnostically Acceptable, Indication-oriented, Patient-specific.
D) Prohibits X-ray use in adults.

C) As Low As Diagnostically Acceptable, Indication-oriented, Patient-specific.

What are the two predominant effects in diagnostic radiology?

A) Photoelectric effect and Compton scattering.
B) Pair production and photoelectric effect.
C) Rayleigh scattering and pair production.
D) Elastic collisions and inelastic impact.

A) Photoelectric effect and Compton scattering.

Why is there NO pair production in dental radiology?

A) Because there are no electrons in teeth.

B) Because it requires materials with Z greater than 100.

C) Because it only occurs with direct current.

D) It requires energies greater than 1022 keV (1.02 MeV).

D) It requires energies greater than 1022 keV (1.02 MeV).

What is braking radiation (bremsstrahlung)?

A) The cooling of the anode after firing X-rays.
B) Radiation emitted when a charged particle decelerates near a nucleus.
C) The spontaneous creation of an electron-positron pair.
D) The complete absorption of a photon in an inner shell.

B) Radiation emitted when a charged particle decelerates near a nucleus.

What is the main benefit of the photoelectric effect in imaging?

A) It decreases the dose on the patient's skin.
B) It produces scattered radiation to protect the operator.
C) It provides the necessary contrast between different tissues.
D) It produces fog and blur on the radiograph.

C) It provides the necessary contrast between different tissues.

Which material is the standard for shielding due to its high Z (82) and density?

A) Aluminum
B) Lead
C) Plastic
D) Copper

B) Lead

What is the main function of the aluminum filter in the X-ray tube?

A) To increase exposure time.

B) To cool down tube components.

C) To absorb low-energy radiation useless for imaging.

D) To scatter radiation in all directions.

C) To absorb low-energy radiation useless for imaging.

In the photoelectric effect, what happens to the incident photon?

A) It is deflected while losing only a small portion of its energy.

B) It transfers all its energy to a bound electron and disappears.

C) It splits into an electron and a positron.

D) It bounces off without giving energy to the atom.

B) It transfers all its energy to a bound electron and disappears.

What does the Half-Value Layer (HVL) represent?

A) The maximum distance traveled by an electron.

B) The time it takes for the tube to cool down to 50%.

C) The thickness of material that reduces the beam intensity by half.

D) The thickness required to absorb 10% of photons.

C) The thickness of material that reduces the beam intensity by half.

Which of these tissues attenuates X-rays the most and appears most radiopaque?

A) Muscle (Zeff ~ 7.6)
B) Water (Zeff ~ 7.5)
C) Bone (Zeff ~ 12.3)
D) Fat (Zeff ~ 6.5)

C) Bone (Zeff ~ 12.3)

Why is Compton scattering harmful in diagnostic radiology?

Question: Why is Compton scattering harmful in diagnostic radiology?

A) Because it generates scattered radiation that degrades image contrast.
B) Because it requires impossible energies in dentistry.
C) Because it destroys the anode of the X-ray tube.
D) Because it absorbs all radiation without letting it pass.

A)) Because it generates scattered radiation that degrades image contrast.