The atomic number of an element is equal to the number of MCQ with Answer and Explanation

Explanation:
LEDs are highly efficient, converting ~80-90% of electrical energy into light, rest heat. Incandescent bulbs ~10% efficient. LED long life, low power. Blue LED Nobel prize 2014.

Explanation:
PE = mgh = 2×10×10 = 200 J.

Explanation:
Ionosphere contains ions and free electrons, reflects radio waves back to Earth, enabling long-distance radio communication. Used in skywave propagation. Troposphere weather layer.