A soap bubble appears coloured due to MCQ with Answer and Explanation

Explanation:
Photovoltaic effect: photons excite electrons in semiconductor, creating voltage. Direct light-to-electricity conversion. Memory tip: 'Photo = light; voltaic = electricity'. Renewable energy principle frequently tested in competitive exams to assess energy conversion understanding.

Explanation:
Leading zeros (before first non-zero digit) are not significant. So 0.0034060: the first non-zero is 3, then 4,0,6 are significant, and the trailing zero after decimal is significant. Thus significant digits are 3,4,0,6,0 — 5 digits. Note: The last zero indicates precision. Answer is 5.

Explanation:
Coulomb's law: E = kq/r² ⇒ E ∝ 1/r². Inverse square law fundamental to electrostatics and gravitation. Memory tip: 'Point charge field: inverse square; double distance ⇒ field becomes 1/4'. Electrostatics concept frequently tested in competitive exams.