A solar water heater cannot be used to get hot water on :
(a) a sunny day
(b) a cloudy day
( c) a hot day
(d) a windy day.

Options

A. a sunny day
B. a cloudy day
C. a hot day
D. a windy day

Answer

To solve the question "A solar water heater cannot be used to get hot water on:", we need to analyze the options provided and understand the working principle of a solar water heater.

### Step-by-Step Solution:

1. **Understanding the Working Principle of a Solar Water Heater**:
- A solar water heater operates by absorbing sunlight (solar radiation) to heat water. The effectiveness of the heater depends on the intensity of sunlight it receives.

2. **Analyzing Each Option**:
- **(a) A sunny day**: On a sunny day, the solar water heater receives maximum sunlight, making it very effective. Therefore, it can be used on a sunny day.
- **(b) A cloudy day**: On a cloudy day, the sunlight is obstructed by clouds. This results in reduced solar radiation reaching the solar water heater, making it less effective or ineffective. Hence, it cannot be used effectively on a cloudy day.
- **(c) A hot day**: A hot day typically indicates clear skies and high temperatures, which usually means that there is plenty of sunlight available. Thus, the solar water heater can be used on a hot day.
- **(d) A windy day**: Wind does not significantly affect the amount of sunlight that reaches the solar water heater. Therefore, it can still be used effectively on a windy day.

3. **Conclusion**:
- Based on the analysis, the solar water heater cannot be used to get hot water on **(b) a cloudy day**.

### Final Answer:
(b) a cloudy day