Some Natural Phenomena — Class 8 Science NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 8 Science chapter "Some Natural Phenomena" — 8 important questions with detailed answers for CBSE board exam preparation.

TL;DR: Free step-by-step NCERT solutions for Class 8 Science chapter "Some Natural Phenomena" — 8 important questions with detailed answers for CBSE board ex…

By Syllab.in · Updated Jun 14, 2026

Key Questions Covered:

Define lightning. Explain how it is formed.
What is thunder? Why does it come after lightning?
How can we calculate the distance of lightning from us using the time interva…
What is an earthquake? What causes it?
What is the Richter scale? What does it measure?
Name three safety precautions to follow during an earthquake.
+ 2 more questions in the full chapter

Solutions Summary:

Question	Status
Define lightning. Explain how it is formed.	✓ Solved
What is thunder? Why does it come after lightning?	✓ Solved
How can we calculate the distance of lightning from us us…	✓ Solved
What is an earthquake? What causes it?	✓ Solved
What is the Richter scale? What does it measure?	✓ Solved
Name three safety precautions to follow during an earthqu…	✓ Solved

Showing 6 of 8 questions

Q1: Define lightning. Explain how it is formed.

Lightning is a sudden electrical discharge between clouds or between clouds and the ground. Formation: Friction between water droplets and ice particles in cumulonimbus clouds creates electric charge separation. Lower part becomes negatively charged, upper part becomes positively charged. When potential difference becomes very large (~100 million volts), electrical breakdown occurs, creating a lightning bolt.

Q2: What is thunder? Why does it come after lightning?

Thunder is the sound produced by lightning. When lightning strikes, it heats the air to ~30,000 K, causing rapid expansion and creating a shock wave. This shock wave is the sound we hear as thunder. Light travels much faster than sound (~300,000 km/s vs ~340 m/s), so we see lightning before hearing thunder. Distance = (time gap) × 340 m/s.

Q3: How can we calculate the distance of lightning from us using the time interval between lightning and thunder?

Step 1: Note the time gap between seeing lightning and hearing thunder (in seconds) Step 2: Use Distance = Speed of sound × Time = 340 m/s × t Example: If time gap is 3 seconds, Distance = 340 × 3 = 1020 m ≈ 1 km. Light travel time is negligible. Divide by 2 if using round-trip time.

Q4: What is an earthquake? What causes it?

An earthquake is the sudden shaking or trembling of the Earth's surface. Causes: (1) Tectonic plate movement—Earth's crust consists of plates that constantly move, (2) Friction between plates builds stress, (3) When stress exceeds the strength of rocks, they suddenly break and slip, (4) This sudden release of energy creates seismic waves that cause shaking and destruction.

Q5: What is the Richter scale? What does it measure?

The Richter scale measures the magnitude (strength) of earthquakes. It ranges from 1 to 9. Magnitude represents the energy released during an earthquake. Scale: 1-3 (not felt), 3-4.5 (slight to moderate damage), 4.5-6 (serious damage), 6-7 (major damage), >7 (devastating). Each unit increase represents ~30 times more energy.

Q6: Name three safety precautions to follow during an earthquake.

(1) Drop, Cover, Hold On: Drop to hands and knees, cover head with arms under a sturdy table or desk. (2) Stay indoors: Avoid going outside where falling debris or power lines are dangerous. (3) Avoid elevators: Use stairs only. (4) Stay away from windows and heavy objects. (5) After the quake, remain alert for aftershocks.

Showing 6 of 8 questions. Visit the full page for complete solutions.