2 simple questions need to clarify (1 Viewer)

[kooltrainer]

1) If 3x10^-19 J are required to remove an electron from a specific metal's surface, calculate threshold frequency and correspoinding threshold wavelength for the light incident upon the metal

ans: frequency = 4.5x10^24 Hz
Wavelength = 6.6 x 10^-7 m

2) Explain how photoelectric effect could be used to measure Planck's constant.

 

[Arowana21]

i am just remember planks constant as 6.626e-34 off the top of my head so if i am wrong tell me.....

Threshold F
Using E=hf - work constant
therefore when E=0
0=(6.626e-34)f - (3e-19)
therefore u should get f= 4.5e14 as threshold frequency

Threshold wavelength
Using c=f lambda
lambda= (3e8)/(4.5e-7)
= 6.67e-7

 

[vds700]

1) If 3x10^-19 J are required to remove an electron from a specific metal's surface, calculate threshold frequency and correspoinding threshold wavelength for the light incident upon the metal

ans: frequency = 4.5x10^24 Hz
Wavelength = 6.6 x 10^-7 m

2) Explain how photoelectric effect could be used to measure Planck's constant.

If u draw a graph of maximum kinetic energy of emitted photoelectrons vs. frequency of incident rays, it will be the graph of KE = hf - W. This is in the form of a straight line graph, y = mx + b, where m is the gradient of the line. Hence in the graph of KE = hf - w, the gradient is h, so u can work out planck's constant. Also, the line cuts the vertical axis at W, so u can also find the work function. Where it cuts the horizontal axis is the threshold frequency of the emitter.