Answer:
The focal lenth (F) =+10.0cm
Explanation:
The formular for combined focal length (F) is given as;
In this question,
F1 = 20cm
F2 = -30cm
Plugging the values into the formuar above,
f = 58.82cm
i.e. the combination behaves as a converging lens (because of the postive sign) of focal length 58.82cm .
To solve this problem we will use the heat transfer equations, to determine the amount of heat added to the body. Subsequently, through the energy ratio given by Plank, we will calculate the energy of each of the photons. The relationship between total energy and unit energy will allow us to determine the number of photons
The mass of water in the soup is 477g
The change in temperate is
Use the following equation to calculate the heat required to raise the temperature:
Here,
m = Mass
c = Specific Heat
The wavelength of the ration used for heating is
The number of photons required is the rate between the total energy and the energy of each proton, then
This energy of the photon is given by the Planck's equation which say:
Here,
h = Plank's Constant
c = Velocity of light
Wavelength
Replacing,
Now replacing we have,
Therefore the number of photons required for heating is