Answer:
c) wafers of crystalline silicon treated with metals that absorb solar radiation and generate electricity
Explanation:
Photovoltaic solar cells are used in solar panels. Most of the photovoltaic cells are made from crystalline silicon.
It has a property using which it converts the light (solar radiation) falling on it to electrical energy. This process occurs due to the photovoltaic effect.
It is a way generating energy without consuming fossil fuels. Thus it reduces the carbon emission and thus plays a major role in environment protection.
Measuring the heat of chemical reactions or physical changes.
Distance/ time = 100/5 = 20 km per hour
The average speed at 5hrs is 20 km per hour.
Answer:B)439.21 Hz
Explanation:
Given
velocity of train 
frequency of train 
speed of sound 
frequency from Doppler effect can be calculated by
