Question

ANSWER 5A, B, AND 6!

5. a) Why do we care about the photoelectric effect? Wait...maybe you don't! Let's try this instead.... The photoelectric effect experiment provides evidence in support of what important physical concept? b) Describe, in your own words, how Einstein's explanation of the photoelectric effect provides evidence in support of this concept. 6. In a photoelectric effect experiment using copper, the maximum kinetic energy of the ejected electrons was measured to be 4.3 ev. What wavelength of light was used in this experiment? The work function of copper is work function of copper is 4.7 ev.

Answer 1

Solution 5(A)- The photo electric effect provides an important physical concept that light (which is considered as wave by many experiments) shows a particle like property.

Solution 5(B)- While performing photo electric experiment intensity of the light was increased but the no. of ejected electrons remained same.while if the light is wave then by increasing its intensity, no. of elejected electrons should increase but this does not happen.

But if we increase the no.of photons (energy of photons should be higher than the work function of the metal) then the no. of ejected photons get increased.so it is clear that photon is interacting directly with the electron means light was showing particle like nature.

Solution 6- Given, work function of the metal(W) = 4.7eV

Maximun kinetic energy of the electron (K.E.) = 4.3 eV

And we know the enegy of the photon $E=hc/\lambda$

Where, hc = 1240 eV-nm

K.E. = E - W or E = K.E.+ W

$hc/\lambda=(4.3+4.7) eV$

$1240 eV-nm/\lambda=9eV$

$\lambda=(1240/9)nm$

$\lambda=137.77nm$ Ans.