Which one of the following statements about X-rays is not true ?
- (a)They have wavelengths of about 1 Å.
- (b)These can be generated by bombarding a metal target by high energy electrons.
- (c)Due to their wavelengths being shorter, these can be used for radar systems.
- (d)These are also used for the treatment of certain forms of cancer.
Correct — C, this statement is not true. X-rays are not used for radar — radar uses radio waves/microwaves (much longer wavelengths). The other statements are all correct: X-rays have wavelengths of about 1 angstrom, are produced by bombarding a metal target with high-energy electrons, and are used to treat certain cancers (radiotherapy).
- (a)wavelengths of about 1 angstrom — True — X-rays have wavelengths of the order of 0.01–10 nm, around 1 angstrom.
- (b)generated by bombarding a metal target with high-energy electrons — True — this is exactly how an X-ray tube works (Coolidge tube).
- (d)used for treatment of certain cancers — True — high-energy X-rays are used in radiotherapy to destroy tumour cells.
X-rays are high-energy electromagnetic waves (wavelength ~1 angstrom) produced when fast electrons strike a heavy-metal target. Their short wavelength lets them penetrate soft tissue (medical imaging) and damage cells (radiotherapy). Radar, by contrast, relies on radio/microwave wavelengths (centimetres), which reflect off aircraft and ships and return echoes — X-rays are unsuitable for it.
Spot the false statement. Radar = radio/microwaves, NOT X-rays. Everything else about X-rays (production, wavelength, cancer therapy) is correct.
- X-rays have wavelengths of about 1 angstrom (0.1 nm).
- They are produced by bombarding a metal target with high-energy electrons.
- They are used in medical imaging and cancer radiotherapy.
- Radar uses radio waves/microwaves, not X-rays.
- Thinking short-wavelength X-rays suit radar — radar needs radio/microwaves.
- Doubting the true statements about X-ray production or therapy.
Asked as the false statement about X-rays, testing EM-spectrum applications.
No directly related past PYQ was found.
- practice — not a real PYQ
Radar systems mainly use which part of the electromagnetic spectrum?
- (a)X-rays
- (b)gamma rays
- (c)radio waves/microwaves
- (d)ultraviolet
Answer(c) radio waves/microwaves.
- practice — not a real PYQ
X-rays in a hospital X-ray tube are produced by
- (a)heating a filament only
- (b)bombarding a metal target with high-energy electrons
- (c)a chemical reaction
- (d)nuclear fission
Answer(b) bombarding a metal target with high-energy electrons.