Answer:
A. K = 0.546 eV
B. cooper and iron will not emit electrons
Explanation:
A. This is a problem about photoelectric effect. Then you have the following equation:
(1)
K: kinetic energy of the ejected electron
Ф: Work function of the metal = 2.48eV
h: Planck constant = 4.136*10^{-15} eV.s
λ: wavelength of light = 410nm - 750nm
c: speed of light = 3*10^8 m/s
As you can see in the equation (1), higher the wavelength, lower the kinetic energy. Then, the maximum kinetic energy is obtained with the lower wavelength (410nm). Thus, you replace the values of all variables :
B. First you calculate the energy of the photon with wavelengths of 410nm and 750nm
You compare the energies E1 and E2 with the work functions of the metals and you can conclude:
sodium = 2.3eV < E1
cesium = 2.1 eV < E1
cooper = 4.7eV > E1 (this metal will not emit electrons)
iron = 4.5eV > E1 (this metal will not emit electrons)
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:
point of support on which a lever rotates.
Explanation:
The fulcrum is the point of support on which a lever rotates. Fulcrum is a pivotal part of simple machines.
The fulcrum provides the platform for a lever to torque.
- The force that opposes motion by the applied force is termed the frictional force.
- Friction is a force that opposes motion.
- The stored energy of an object is its potential energy.
- The potential energy is the energy due to the position of a body.
- The distance an object moves when doing work is termed its displacement.
To look for displacement, just draw a vector from your beginning stage to your last position and settle for the length of this line. So we begin by drawing a line to the north which is 30 ft, since it is north, the line is going up, then it move 5 ft to the south, so put a line going down, so we are in 25 ft, North so that would be the answer.
C
Because in my opinion they do bending of a light wave as it passes at an angle from one medium to another.
