Answer:
Part a)

Part b)

Explanation:
As we know that capacitor plate is connected across 2.1 V and after charging it is disconnected from the battery
So here we can say that charge on the plates will remain conserved
So we will have

now dielectric is removed between the plates of capacitor
so new potential difference between the plates




Part b)
Now the capacitor plates are again isolated and unknown dielectric is inserted between the plates
So again charge is same so potential difference is given as




Threshhold frequency is defined as the minimum light frequency necessary to start photo-electric emission from the surface. This frequency is just effecient enough to emit electrons without any additional force or energy. this minimum frequency creates the necessary result that is sought by the person. The photo electric emission for certain metals can occir with threshhold frequency. The importance of this threshhold frequency lies in the fact that this has been used to create numerous instruments like amplifiers for use of people.
Answer:
Voltage in the primary winding of the coil is 3.9 V
Explanation:
As we know by the principle of transformer we have

here we know that



now we have


Elastic potential energy.
When you stretch a rubber band it has the "potential" to do work, to fly in a given direction. In doing so it changes it's elastic potential energy to kinetic energy.
Nuclear fusion is a reaction in which two or more atomic nuclei come very close and then collide at a very high speed and join to form a new nucleus. This process is important to stars because they get their energy from the nuclear fusion process