UPSC Prelims 2008 Q134: Science & Technology – Physics
Assertion (A): Radio waves bend in a magnetic field.
Reason (R): Radio waves are electromagnetic in nature.
- (a) Both A and R are individually true and R is the correct explanation of A
- (b) Both A and R are individually true but R is not the correct explanation of A
- (c) A is true but R is false
- (d) A is false but R is true
Answer: (d) A is false but R is true
Explanation
Checking an Assertion-Reason pair on radio waves and magnetic fields
Assertion (A): Radio waves bend in a magnetic field.
Reason (R): Radio waves are electromagnetic in nature.
| Statement | Verdict | Reason |
|---|---|---|
| Assertion (A) | False | Radio waves, being uncharged electromagnetic waves, do NOT bend in a magnetic field the way charged particles do |
| Reason (R) | True | Radio waves ARE indeed electromagnetic in nature, part of the electromagnetic spectrum |
Why A is false but R is true:
| Point | Detail |
|---|---|
| Magnetic field bending | Affects charged particles, not neutral EM waves like radio waves |
| Radio waves' nature | Genuinely electromagnetic, but this fact alone doesn't cause magnetic bending |
Answer: (d) A is false but R is true.
Why each option is right or wrong
- (a) Incorrect. A is false (radio waves don't bend in a magnetic field), so this option is wrong.
- (b) Incorrect. A is false, not true, so this option is also wrong.
- (c) Incorrect. A is false, not true, so this doesn't match either.
- (d) CORRECT. A is false (radio waves don't bend in a magnetic field), while R is true (radio waves are indeed electromagnetic in nature).
Key point
Radio waves do NOT bend in a magnetic field (making the Assertion false), since they are uncharged — but they ARE genuinely electromagnetic in nature (making the Reason true).
Remember
Radio waves do NOT bend in a magnetic field (Assertion false) — but they ARE electromagnetic in nature (Reason true).
Common mistakes
- Confusing the behaviour of charged particles (which do bend in magnetic fields) with uncharged electromagnetic waves like radio waves.
- Assuming 'electromagnetic nature' automatically implies magnetic-field bending.
- Not distinguishing between a wave's fundamental nature and its specific physical behaviour in a field.
Exam tip
Being 'electromagnetic' does NOT mean a wave bends in a magnetic field — that's a property of CHARGED particles, not neutral EM waves.
Sources
- NCERT Class XII Physics — Electromagnetic Waves
- NCERT Class XII Physics — Moving Charges and Magnetism