The correct option is D.
In the equation given above, Q stands for quantity of heat and J stands for Joule, which is the unit for measuring heat and the quantity of the heat given is negative. The negativity of the value of the heat given shows that the reaction is an exothermic reaction.
There are basically two types of reaction in term of heat involved, these are endothermic and exothermic reaction. An exothermic reaction is a type of reaction which gives out heat to the environment. Because of this, the energy value of the product is always lesser than that of the reactant. The difference between the energy of the products and the energy of the reactants is called enthalpy change of the reaction. For an exothermic reaction, the enthalpy change is always negative.
Answer:
1. The frequency of the incident light must be equal to or greater than the threshold frequency of the photons before emission could take place.
2. The intensity of the incident light is proportional to the amount of photons released. The higher the intensity of light, the greater the amount of photons ejected.
Explanation:
1. Photoelectric effect is the process by which light with sufficient frequency falls on the surface of a material, e.g metal, to emit electrons. The incident light must have a minimum value of required frequency for the electrons to be ejected. This energy is termed work function which is a function of frequency.
So for emission to take place, the frequency of the incident light must be equal to or greater than the threshold frequency of the photons.
2. The intensity of light is a measure of the amount of light per unit area. When the intensity of incident light increases, the probability that photons would be released increases. The intensity of the incident light is proportional to the amount of photons released.
Answer:250N
Explanation:
Spring constant=500N/m
Extension=0.5m
Weight=spring constant x extension
Weight=500 x 0.5
Weight=250
Weight is 250N
Answer:
(a) 294 J
(b) 229591.84 kg
Explanation:
height, h = 30 m
g = 9.8 m/s^2
(a) U = m x g x h
U = 1 x 9.8 x 30
U = 294 J
(b) Let the mass of water is m
U = m x g xh
80% of this energy per second is generating power
0.8 x m x 9.8 x 30 = 54 x 10^6
m = 229591.84 kg
Thus, the mass of water required is 229591.84 kg.
