JEE Main 2020 · 5 September · evening · Single correct · +4 / −1
The correct match between the entries in column I and column II are :
| I | II |
|---|---|
| Radiation | Wavelength |
| (a) Microwave | (i) 100 m |
| (b) Gamma rays | (ii) 10 –15 m |
| (c) A.M. radio waves | (iii) 10 –10 m |
| (d) X-rays | (iv) 10 –3 m |
- (a) (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
- (b) (a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
- (c) (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
- (d) (a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)
Answer and solution
Answer (b) (a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
Solution
Physics sir · 3 steps
Line both lists up from longest to shortest wavelength and the matching falls into place.
- Order the radiations. In the spectrum, wavelength falls in this order: radio waves, microwaves, infrared, visible, ultraviolet, X-rays, gamma rays. So among these four, A.M. radio is the longest and gamma rays are the shortest.
- Order the wavelengths. Sort the given values from largest to smallest: 100 m > 10⁻³ m > 10⁻¹⁰ m > 10⁻¹⁵ m. Pair the two ordered lists one to one.
Radiation Typical wavelength Matches A.M. radio waves hundreds of metres (i) 100 m Microwave 1 mm to 0.1 m (iv) 10⁻³ m X-rays about 10⁻⁸ to 10⁻¹² m (iii) 10⁻¹⁰ m Gamma rays below about 10⁻¹² m (ii) 10⁻¹⁵ m - So. The match is (a)-(iv), (b)-(ii), (c)-(i), (d)-(iii), which is option (b).
The idea to keep. For any spectrum-matching question, write the order radio, micro, IR, visible, UV, X, gamma once, then sort the given numbers and pair them off in order.
Answer from the NTA final answer key. Solution by PrepWiser.