Which one of the following types of radiations has the smallest wavelength?
- A.Microwaves
- B.Infra-red
- C.Visible light
- D.X-rays
Correct answer
Explanation
The correct answer is D, X-rays. Of the four, X-rays lie farthest towards the short-wavelength, high-energy end of the electromagnetic spectrum.
All electromagnetic waves travel at the speed of light in vacuum but differ in wavelength. In order of decreasing wavelength the spectrum runs: radio waves, microwaves, infra-red, visible light, ultraviolet, X-rays and gamma rays. X-rays have wavelengths of roughly 0.01 to 10 nanometres, thousands of times shorter than visible light (about 400 to 700 nanometres). Shorter wavelength means higher frequency and more energy per photon, which is why X-rays pass through soft tissue and are used in medical imaging, while only gamma rays are shorter still.
A is wrong because microwaves have wavelengths from about a millimetre to tens of centimetres. B is wrong because infra-red waves are longer than visible light. C is wrong because visible light, though shorter than infra-red, is far longer than X-rays.
Exam tip: Radio, micro, infra-red, visible, UV, X-ray, gamma: wavelength falls and energy rises along this order.
Practice Questions
View allThe instrument used for detecting the presence of electric current in a circuit is
- A.Refractometer
- B.Galvanometer
- C.Viscometer
- D.Diffractometer
Show answer
A galvanometer detects whether a small electric current is flowing in a circuit and shows its direction. A moving-coil galvanometer has a coil placed between the poles of a magnet.
Read the full explanation →Reverberation is a phenomenon associated with a
- A.multiple refraction of sound.
- B.multiple reflection of sound.
- C.single refraction of sound.
- D.single reflection of sound.
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Reverberation is the persistence of sound in a hall after the source has stopped, caused by repeated reflections from the walls, ceiling and floor.
Read the full explanation →Which one of the following is NOT a basic property of electric charge ?
- A.Charges can be added
- B.Charge is conserved
- C.Charge on a body is always an integral multiple of an electron or a proton charge
- D.Charges can be created and destroyed in an isolated system
Show answer
This goes against the conservation of charge: the total charge of an isolated system always stays the same. Electric charge has three basic properties.
Read the full explanation →Which of the following organelles have their own DNA and ribosomes?
- A.Endoplasmic reticulum and Golgi bodies
- B.Mitochondria and Chloroplast
- C.Endoplasmic reticulum and cytoskeleton
- D.Cell wall and nucleolus
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These two organelles carry their own circular DNA and their own small (70S) ribosomes, so they can make some of their own proteins.
Read the full explanation →Which one of the following statements is NOT correct ?
- A.All proteins are enzymes
- B.Mostly enzymes are proteins
- C.All fats are energy rich compounds
- D.Glucose is a common carbohydrate
Show answer
This statement is false: enzymes are mostly proteins, but most proteins are not enzymes. Proteins do many jobs in the body.
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