. A new programming language requires variable names to start with a letter (upper or lowercase), which can be followed by lette
2 answers:
Answer:
Explanation:
Total letters available on the keyboard = 26
Doubling this amount to account for both upper and lower case letters.
Therefore, Total characters (Upper + Lower Case) = 52 characters
Total numbers on keyboard (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) = 10 characters
Underscore = 1 character
Thus, Total allowed characters = 52 + 10 + 1 = 63
This is a problem of the permutation as order of the characters results in a different name.
Our file name should be of atleast 3 and smaller than 7 (i.e. 6) characters
Therefore, total possible permutations can be obtained by subtraction permutation of 2 characters from the permutations of 6 characters.
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a) Zinc (work function: 4.3 eV)
The equation for the photoelectric effect is:
(1)
where
is the energy of the incident photon, with
h = Planck constant
c = speed of light
= wavelength
= work function of the metal
K = maximum kinetic energy of the photoelectrons emitted
The stopping potential (V) is the potential needed to stop the photoelectrons with maximum kinetic energy: so, the corresponding electric potential energy must be equal to the maximum kinetic energy,
So we can rewrite (1) as
where we have:
V = 1.93 V
e is the electron charge
First of all, let's find the energy of the incident photon:
Converting into electronvolts,
And now we can solve eq.(1) to find the work function of the metal:
so, the metal is most likely zinc, which has a work function of 4.3 eV.
b) The stopping potential is still 1.93 V
Explanation:
The intensity of the incident light is proportional to the number of photons hitting the surface of the metal. However, the energy of the photons depends only on their frequency, so it does not depend on the intensity of the light. This means that the term E in eq.(1) does not change.
Moreover, the work function of the metal is also constant, since it depends only on the properties of the material: so is also constant in the equation. As a result, the term (eV) must also be constant, and therefore V, the stopping potential, is constant as well.