Introduction:
Solar energy is converted into chemical energy in the form of adenosine triphosphate (ATP) through a process called photosynthesis. Photosynthesis occurs in the chloroplasts of plant cells, where sunlight, carbon dioxide, and water are converted into glucose and oxygen. This energy-rich glucose molecule is then broken down in the mitochondria to produce ATP, which is used as the primary energy source for cellular activities.

1. Mitochondria:
Mitochondria are known as the "powerhouses" of the cell because they are responsible for producing ATP through cellular respiration. During cellular respiration, glucose and oxygen are broken down in a series of enzymatic reactions to release energy. This process occurs in the mitochondria and is known as aerobic respiration. The energy released is used to generate ATP, which can be used by the cell for various functions such as muscle contraction, active transport, and synthesis of macromolecules.

2. Ribosomes:
Ribosomes are cellular structures responsible for protein synthesis. They are not directly involved in the conversion of solar energy into ATP. However, the energy stored in ATP is required for protein synthesis to occur. ATP provides the necessary energy for the activation of amino acids and the formation of peptide bonds during translation. Ribosomes use this energy to read the genetic code and assemble amino acids into proteins, which are essential for the structure and function of cells.

3. Chloroplasts:
Chloroplasts are the organelles responsible for photosynthesis in plant cells. They contain a green pigment called chlorophyll, which absorbs sunlight energy. During photosynthesis, solar energy is harnessed to convert carbon dioxide and water into glucose and oxygen. This process occurs in the thylakoid membranes of the chloroplasts, where chlorophyll molecules capture light energy and convert it into chemical energy in the form of ATP and NADPH. These energy-rich molecules are then used to fuel the Calvin cycle, where carbon dioxide is fixed and converted into glucose.

4. Peroxisomes:
Peroxisomes are involved in various metabolic processes, including the breakdown of fatty acids and the detoxification of harmful substances. However, they are not directly involved in the conversion of solar energy into ATP. ATP is primarily produced in the mitochondria through cellular respiration and in the chloroplasts through photosynthesis.

In conclusion, solar energy is converted into chemical energy in the form of ATP through the processes of photosynthesis and cellular respiration. Chloroplasts capture sunlight and convert it into ATP, which is then used by mitochondria to power cellular activities. Ribosomes utilize ATP for protein synthesis, while peroxisomes are involved in other metabolic processes but not in the direct conversion of solar energy into ATP.

Option (3) Chloroplast is the correct answer.