Which one of the following wavelength radiations may correspond to an X-ray?
- (a)1 nm
- (b)10 nm
- (c)100 nm
- (d)300 nm
Correct — A, 1 nm. X-rays occupy the very-short-wavelength band of the electromagnetic spectrum, roughly 0.01 nm to 10 nm. A wavelength of 1 nm sits well inside that band, so it is the only listed value that can cleanly be an X-ray. The other choices climb into the ultraviolet region (~10-400 nm), which has longer wavelengths and lower photon energy than X-rays.
- (b)10 nm — 10 nm sits right at the soft-X-ray / extreme-ultraviolet boundary — it is the ambiguous upper edge of the X-ray band rather than a clean X-ray value, so 1 nm is the safer textbook answer.
- (c)100 nm — 100 nm is ultraviolet (UV spans roughly 10-400 nm). It is about a hundred times longer than a typical X-ray wavelength, so it is far too long to be an X-ray.
- (d)300 nm — 300 nm is near-ultraviolet, just short of the violet edge of visible light (~400 nm). Its wavelength is hundreds of times that of an X-ray, so it cannot be one.
The electromagnetic spectrum runs from long-wavelength radio waves down to ultra-short gamma rays. In order of decreasing wavelength: radio > microwave > infrared > visible (~400-700 nm) > ultraviolet (~10-400 nm) > X-rays (~0.01-10 nm) > gamma rays. Wavelength and frequency are inversely related (c = f lambda), and photon energy rises with frequency (E = hf), so X-rays are far more energetic than ultraviolet or visible light.
To place any wavelength, anchor on the visible window (about 400-700 nm). Anything a little shorter than violet, down to ~10 nm, is ultraviolet; shorter still (~0.01-10 nm) is X-ray. So 300 nm and 100 nm land in the UV, while 1 nm is ten to a few-hundred times shorter and lands in the X-ray band.
- X-rays span roughly 0.01-10 nm; ultraviolet roughly 10-400 nm; visible light 400-700 nm.
- Wavelength and frequency are inversely related (c = f lambda); shorter wavelength means higher frequency and higher photon energy (E = hf).
- Gamma-ray and X-ray wavelength bands overlap; they are conventionally separated by ORIGIN — gamma rays from the atomic nucleus, X-rays from electron transitions or bremsstrahlung.
- 1 nm equals 10 angstrom; the angstrom (0.1 nm) is the traditional unit for X-ray wavelengths and atomic spacings.
- Assuming a bigger number of nanometres means 'more energetic' — it is the opposite; shorter wavelength means higher energy.
- Forgetting that 10 nm sits on the soft-X-ray / extreme-UV boundary, so 1 nm is the cleaner X-ray value.
The EM spectrum is asked as 'which radiation has this wavelength/frequency' or 'arrange in increasing wavelength/energy' — anchor on the visible band (400-700 nm).
Cobalt-60 is commonly used in radiation therapy because it emits
- (a) alpha rays
- (b) beta rays
- (c) gamma rays
- (d) X-rays
Answer(c) gamma rays
Same idea — identifying high-energy electromagnetic radiation. There the task is to know Cobalt-60 emits gamma rays (not X-rays); here it is placing 1 nm in the X-ray band. Both reward a firm grip on the short-wavelength, high-energy end of the EM spectrum, where X-rays and gamma rays sit.
- practice — not a real PYQ
Which one of the following electromagnetic radiations has the shortest wavelength?
- (a)Radio waves
- (b)Infrared
- (c)Visible light
- (d)Gamma rays
Answer(d) Gamma rays — they lie at the short-wavelength, high-frequency end of the electromagnetic spectrum.
- practice — not a real PYQ
Ultraviolet radiation lies between which two regions of the electromagnetic spectrum?
- (a)Infrared and microwave
- (b)Visible light and X-rays
- (c)Radio and infrared
- (d)Gamma rays and X-rays
Answer(b) Visible light and X-rays — UV (~10-400 nm) is shorter than visible but longer than X-rays.