Question

Which of the following reaction(s) involves absorption of light to initiate?

• A. Respiration
• B. Photosynthesis
• C. Combustion
• D. Photochemical decomposition

Answer 1

Answer: (B), (D)

The correct options are
B

Photosynthesis

D

Photochemical decomposition

The reaction that is initiated by the absorption of light is known as the photochemical reaction.

Photosynthesis is the process in which carbon dioxide ($C{O}_2$), water ($H_{2}O$) reacts in the presence of sunlight to form carbohydrate (glucose) and oxygen ($O_2$) This reaction involves the absorption of sunlight to initiate.

$6C{O}_2\left(aq\right)+6H_{2}O\left(l\right)\stackrel{Sunlight}{\to }{C}_6{H}_{12}{O}_6\left(aq\right)+6O_2\left(aq\right)$

Photochemical decomposition is the type of photochemical reaction that involves absorption of light to initiate.

Example:- $2AgBr\left(s\right)\stackrel{Sunlight}{\to }2Ag\left(s\right)+B{r}_2\left(g\right)$

Respiration is the opposite of photosynthesis and instead of absorption of energy (light), it releases energy in the form of heat.

Combustion is the burning of any substance in the presence of oxygen and this reaction generates a large amount of heat and light energy.