The answer & explanation for this question is given in the attachment below.
Answer:
Lithium
Explanation:
The equation for the photoelectric effect is

where
is the energy of the incident photon, with
h being the Planck constant
c is the speed of light
is the wavelength of the photon
is the work function of the metal (the minimum energy needed to extract the photoelectron from the metal)
is the maximum kinetic energy of the emitted photoelectrons
In this problem, we have
is the wavelength of the incident photon
is the maximum kinetic energy of the electrons
First of all we can find the energy of the incident photon

Converting into electronvolts,

So now we can re-arrange the equation of the photoelectric effect to find the work function of the metal

So the metal is most likely Lithium, which has a work function of 2.5 eV.
Answer:
I think deposition of C is the oldest deposit
Answer:
The value is 
Explanation:
From the question we are told that
The relationship between the number of whooping cranes and the number of decades is 
The exponential relationship is
Now from the given equation we have that


So comparing this equation obtained an the given exponential relationship we have that




Answer:

Explanation:
Given that
Radius =r
Electric filed =E
Q=Charge on the ring
The electric filed at distance x given as

For maximum condition



For maximum condition




At
the electric field will be maximum.