Solar Radiation and Energy

 The sun is composed primarily of the chemical elements hydrogen and helium. They account for 74.9% and 23.8% of the mass of the Sun in the photosphere, respectively. All heavier elements, called metals in astronomy, account for less than 2% of the mass. The most abundant metals are oxygen (roughly 1% of the Sun's mass), carbon (0.3%), neon (0.2%), and iron (0.2%).

1 only

This is the correct option. Sun is the ultimate source of energy for all living organisms. In plants, solar energy is captured by the leaves and stored in the form of food. 

The Sun's energy is produced by nuclear fusion of light nuclei - specifically, hydrogen nuclei (protons) fusing to form helium in the core. This process releases enormous energy because the mass of helium produced is slightly less than the mass of four hydrogen nuclei, with the difference converted to energy (E=mc²).

Source of energy in an ecosystem is the sun. 

The Sun creates energy through nuclear fusion, where hydrogen nuclei combine to form helium, releasing enormous energy. Nuclear fission splits atoms and is used in power plants on Earth. Conduction and radiation are heat transfer methods, not energy production processes.

Correct option is (3).

The component of sunlight that carries heat radiation is infrared radiation.

The phrase 'source OF' is the correct preposition to use when indicating origin or cause. 'The sun is the main source OF energy' shows that energy originates from the sun. This is a fixed collocation in English.

Insolation is the specific technical term for incoming solar radiation reaching Earth's surface. Radiant energy is too generic and could refer to any electromagnetic radiation. Sunshine is an informal term. Terrestrial radiation refers to heat radiation emitted by Earth itself, not incoming solar energy.

Solar heat reaches Earth primarily through radiation across the vacuum of space. Minor conduction occurs in the atmosphere, and atmospheric convection currents distribute heat. Since all three processes contribute to varying degrees, Option D is technically correct. Radiation is the dominant mechanism.

The sun's energy is primarily produced by nuclear fusion, where hydrogen nuclei combine to form helium in the sun's core. This process releases enormous energy in the form of light and heat.

Plants are very inefficient at capturing solar energy. Only about 1% of the solar energy that reaches leaves is actually converted into chemical energy during photosynthesis. The rest is reflected, transmitted as heat, or lost in other metabolic processes.

The Sun is the ultimate source of energy for Earth's ecosystems. All energy flows - whether through plants (producers), animals (consumers), or decomposers - can be traced back to solar energy captured during photosynthesis. Without the Sun, there would be no energy available to sustain life.

Artificial satellites primarily use solar cells to generate electricity because they can operate continuously in space where sunlight is abundant. Solar cells convert sunlight directly into electrical energy. Dry cells and voltaic cells would run out quickly, while dynamos require mechanical input.