• **1 Gy = 100 rad** (absorbed dose, easy to remember)
• **1 Sv = 100 rem** (equivalent dose, same pattern)
• **1 Ci = 37 GBq** (activity, exactly by definition)
• **For X-rays: 1 Gy = 1 Sv** (Q factor = 1)
• **For alpha: 1 Gy = 20 Sv** (Q factor = 20, 20× more damaging)
• **Chest X-ray ≈ 0.1 mSv** (memorize this benchmark)
• **Annual background ≈ 2.4 mSv** (global average)

• **Absorbed Dose (Gy, rad):** Physical energy deposited, no biology
• **Equivalent Dose (Sv, rem):** Biological damage, includes Q factor
• **Activity (Bq, Ci):** Radioactive decay rate, not exposure
• **Exposure (R):** Old unit, X-rays in air only, rarely used
• **Never convert between categories** without physics calculations

• **X-rays & gamma:** Q = 1 (so 1 Gy = 1 Sv)
• **Beta particles:** Q = 1 (electrons)
• **Neutrons:** Q = 5-20 (energy-dependent)
• **Alpha particles:** Q = 20 (most damaging per Gy)
• **Heavy ions:** Q = 20

• **Never assume Gy = Sv** without knowing radiation type (only true for X-rays/gamma)
• **Can't convert Bq to Gy** without isotope, energy, geometry, time, mass data
• **Roentgen ONLY for X/gamma in air** — doesn't work for tissue, alpha, beta, neutrons
• **Don't confuse rad (dose) with rad (unit of angle)** — completely different!
• **Activity (Bq) ≠ Dose (Gy/Sv)** — high activity doesn't mean high dose without geometry
• **1 mSv ≠ 1 mGy** unless Q=1 (for X-rays yes, for neutrons/alpha NO)

Energy deposited in matter

Units: Gray (Gy), rad, J/kg

The amount of radiation energy absorbed per kilogram of tissue. Purely physical—doesn't account for biological effects.

Example: Chest X-ray: 0.001 Gy (1 mGy) | CT scan: 0.01 Gy (10 mGy) | Lethal dose: 4-5 Gy

• 1 Gy = 100 rad
• 1 mGy = 100 mrad
• 1 Gy = 1 J/kg

Biological effect on tissue

Units: Sievert (Sv), rem

Biological effect of radiation, accounting for different damage from alpha, beta, gamma, neutron radiation types.

Example: Annual background: 2.4 mSv | Chest X-ray: 0.1 mSv | Occupational limit: 20 mSv/year | Lethal: 4-5 Sv

• 1 Sv = 100 rem
• For X-rays: 1 Gy = 1 Sv
• For alpha: 1 Gy = 20 Sv

Decay rate of radioactive material

Units: Becquerel (Bq), Curie (Ci)

Number of radioactive atoms decaying per second. Tells you how 'radioactive' material is, NOT how much radiation you receive.

Example: Human body: 4,000 Bq | Banana: 15 Bq | PET scan tracer: 400 MBq | Smoke detector: 37 kBq

• 1 Ci = 37 GBq
• 1 mCi = 37 MBq
• 1 µCi = 37 kBq

Ionization in air (X-rays/gamma only)

Units: Roentgen (R), C/kg

Amount of ionization produced in air by X-rays or gamma rays. Older measurement, rarely used today.

Example: Chest X-ray: 0.4 mR | Dental X-ray: 0.1-0.3 mR

• 1 R = 0.000258 C/kg
• 1 R ≈ 0.01 Sv (rough approximation)

X-rays

Working late, Röntgen noticed fluorescent screen glowing across the room despite his cathode ray tube being covered. First X-ray image: his wife's hand with bones and wedding ring visible. She exclaimed 'I have seen my death!' Won first Nobel Prize in Physics (1901).

Revolutionized medicine overnight. By 1896, doctors worldwide used X-rays to locate bullets and set broken bones.

Radioactivity

Left uranium salts on wrapped photographic plate in drawer. Days later, plate was fogged—uranium emitted radiation spontaneously! Shared 1903 Nobel Prize with Curies. Accidentally burned himself by carrying radioactive materials in vest pocket.

Proved atoms weren't indivisible—they could spontaneously break down.

Polonium and Radium

Processed tons of pitchblende by hand in cold Parisian shed. Discovered polonium (named after Poland) and radium (glows blue in dark). Kept radium vial by bedside 'because it looks so pretty at night.' Marie won Nobel Prizes in Physics AND Chemistry—only person to win in two sciences.

Radium became basis for early cancer therapy. Marie died 1934 from radiation-induced aplastic anemia. Her notebooks are still too radioactive to handle—stored in lead-lined boxes.

Alpha and Beta radiation

Discovered radiation came in types with different penetrating abilities: alpha (stopped by paper), beta (penetrates further), gamma (discovered 1900 by Villard). Won 1908 Nobel Prize in Chemistry.

Laid groundwork for understanding nuclear structure and modern concept of equivalent dose (Sievert).

Minimize exposure time

Work quickly near radiation sources. Halve the time = halve the dose.

Maximize distance from source

Radiation follows inverse-square law: double distance = ¼ dose. Step back!

Use appropriate barriers

Lead for X-rays/gamma, plastic for beta, paper for alpha. Concrete for neutrons.

Verdict: FALSE

You're constantly exposed to natural background radiation (~2.4 mSv/year) with no harm. Low doses from medical imaging carry tiny risks, usually justified by diagnostic benefit.

Verdict: FALSE

Average dose from living near nuclear plant: <0.01 mSv/year. You get 100× more radiation from natural background. Coal plants emit more radiation (from uranium in coal)!

Verdict: FALSE

Airport backscatter scanners: <0.0001 mSv per scan. You'd need 10,000 scans to equal one chest X-ray. The flight itself gives 40× more radiation.

Verdict: EXAGGERATED

Single diagnostic X-ray: <5 mSv, usually <1 mSv. Fetal harm risk begins above 100 mSv. Still, inform doctor if pregnant—they'll shield abdomen or use alternatives.

Verdict: DANGEROUS OVERSIMPLIFICATION

Only true for X-rays and gamma rays (Q=1). For neutrons (Q=5-20) or alpha particles (Q=20), you must multiply by Q factor. Never assume Q=1 without knowing radiation type!

Verdict: TRUE BUT NEGLIGIBLE

True that isotopes were detected globally, but doses outside exclusion zones were tiny. Most of world received <0.001 mSv. Natural background is 1000× higher.

Only if you know the radiation type. For X-rays and gamma rays: 1 Gy = 1 Sv (Q=1). For alpha particles: 1 Gy = 20 Sv (Q=20). For neutrons: 1 Gy = 5-20 Sv (energy-dependent). Never assume Q=1 without verification.

No, not directly. Becquerel measures radioactive decay rate (activity), while Gray/Sievert measure absorbed dose. Conversion requires: isotope type, decay energy, source geometry, shielding, exposure time, and tissue mass. This is a complex physics calculation.

Because radiation effects depend on multiple factors: (1) Energy deposited in tissue (Gray), (2) Biological damage from different radiation types (Sievert), (3) How radioactive the source is (Becquerel), (4) Historical air ionization measurement (Roentgen). Each serves a different purpose.

No. Average annual background radiation is 2.4 mSv globally. A chest X-ray is 0.1 mSv. Occupational limits are 20 mSv/year (averaged). Acute radiation sickness begins around 1,000 mSv (1 Sv). Single mSv exposures from medical imaging carry tiny cancer risks, usually justified by diagnostic benefit.

CT scans involve higher doses (2-20 mSv) but are life-saving for trauma, stroke, cancer diagnosis. Follow ALARA principle: ensure scan is medically justified, ask about alternatives (ultrasound, MRI), avoid duplicate scans. Benefits usually far outweigh small cancer risk.

Rad measures absorbed dose (physical energy). Rem measures equivalent dose (biological effect). For X-rays: 1 rad = 1 rem. For alpha particles: 1 rad = 20 rem. Rem accounts for the fact that alpha particles cause 20× more biological damage per unit energy than X-rays.

Her notebooks, lab equipment, and furniture are contaminated with radium-226 (half-life 1,600 years). After 90 years, they're still highly radioactive and stored in lead-lined boxes. Requires protective gear and dosimetry to access. Will remain radioactive for thousands of years.

No. Average dose from living near nuclear plant: <0.01 mSv/year (measured by monitors). Natural background radiation is 100-200× higher (2.4 mSv/year). Coal plants emit more radiation due to uranium/thorium in coal ash. Modern nuclear plants have multiple containment barriers.