The sun delivers roughly 1kwm2 of power to the earth’s surface. a parabolic mirror with a 1.5 m radius is used to focus this energy onto a beaker containing 2 l of water. estimate the time taken by the mirror to rise the temperature of water by 60°c, assuming cp, m= 75291 j k mol and ignoring energy losses to the surroundings.

Explanation:

The amount of heat required by water to increase its temperature by ,

                       q = .............. (1)    

where,       q = heat gained  

                 m= mass in kg,

                  c = specific heat (in terms of )                                                          

                dT = increase in temperature

Now, putting the given values into equation ( 1) as follows.

                 q =

                     =

                    = 4517.46 kJ

Now,  surface area of the mirror, A =

where,            r = radius of the mirror

                         = 1.5 m

Therefore,     area =  

                              =

                              = 7.065

As, 1 means = 1 kJ per second per square meter surface area.                  (as 1 W = 1 J/s)

Hence, amount of energy focused by mirror = incidence rate of solar energy x surface area of mirror

                    =

                   = 3.14 kJ s-1

Therefore, the mirror focuses 3.14 kJ energy per second

Time required by the mirror to focus 4517.46 kJ  energy =

                          = 1438.68 seconds

or,                     =

                         = 23.97 min

Thus, we can conclude that the time taken by the mirror to rise the temperature of water is 23.97 min.

b is the correct

idk what is it? is this a question that you know the answer or u dont