A) We want to find the work function of the potassium. Apply this equation:
E = 1243/λ - Φ
E = energy of photoelectron, λ = incoming light wavelength, Φ = potassium work function
Given values:
E = 2.93eV, λ = 240nm
Plug in and solve for Φ:
2.93 = 1243/240 - Φ
Φ = 2.25eV
B) We want to find the threshold wavelength, i.e. find the wavelength such that the energy E of the photoelectrons is 0eV. Plug in E = 0eV and Φ = 2.25eV and solve for the threshold wavelength λ:
E = 1243/λ - Φ
0 = 1243/λ - Φ
0 = 1243/λ - 2.25
λ = 552nm
C) We want to find the frequency associated with the threshold wavelength. Apply this equation:
c = fλ
c = speed of light in a vacuum, f = frequency, λ = wavelength
Given values:
c = 3×10⁸m/s, λ = 5.52×10⁻⁷m
Plug in and solve for f:
3×10⁸ = f(5.52×10⁻⁷)
f = 5.43×10¹⁴Hz
For this problem, we use the decay equation which is expressed as:
An = (Ao)e^-kt
where An is the amount left in t time, Ao is the initial amount and k is a constant.
We first calculate the value of k as follows:
An = (Ao)e^-kt
0.5 = e^-k(8)
k = 0.087
We calculate the time as follows:
An = (Ao)e^-kt
15.625 = 250e^-0.087t
t = 31.87 days
Answer:
a wheel and axle can also serve as a force multiplier, according to Science Quest from Wiley. If a wheel is attached to an axle, and a force is used to turn the wheel, the rotational force, or torque, on the axle is much greater than the force applied to the rim of the wheel.
Explanation:
D. A magnetic field created by the electric current causes the compass needle to move.
Answer:
You could claim that Pluto is a planet as it rotates around our sun.
Explanation:
Hope that helps :)