Physical Sciences Flashcards
7 cards from real STP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Physical Sciences flashcards as text
Which type of electromagnetic radiation has the shortest wavelength used in medical imaging?
Answer: X-ray
X-rays have wavelengths in the range of 0.01–10 nm, making them the shortest wavelength radiation routinely used in medical imaging.
What is the half-life of a radioactive isotope if 75% of a sample decays in 20 years?
Answer: 10 years
If 75% decays, 25% remains; since (1/2)^2 = 0.25, two half-lives have passed, so the half-life is 20/2 = 10 years.
In a semiconductor detector for ionising radiation, what charge carriers are collected?
Answer: Electrons and holes
Ionising radiation creates electron-hole pairs in the semiconductor, and these charge carriers are swept to electrodes by an applied electric field.
What physical principle underlies Magnetic Resonance Imaging (MRI)?
Answer: Nuclear spin precession in a magnetic field
MRI exploits the precession of hydrogen nuclei (protons) aligned in a strong magnetic field when perturbed by a radiofrequency pulse.
Which law states that the pressure of a fixed mass of gas is inversely proportional to its volume at constant temperature?
Answer: Boyle's Law
Boyle's Law states that P ∝ 1/V at constant temperature, meaning pressure and volume are inversely proportional for an ideal gas.
What is the unit of absorbed radiation dose in the SI system?
Answer: Gray (Gy)
The Gray (Gy) is the SI unit of absorbed dose, defined as 1 joule of energy deposited per kilogram of tissue.
A photon travels through a medium with refractive index 1.5. What is its speed in that medium given that c = 3×10⁸ m/s?
Answer: 2×10⁸ m/s
Speed in medium = c/n = 3×10⁸ / 1.5 = 2×10⁸ m/s.