Question

50% of the X-ray coming from a Coolidge tube is able to pass through a 0.1 mm thick aluminium foil. If the potential difference between the target and the filament is increased, the fraction of the X-ray passing through the same foil will be

• A. 0%
• B. < 50%
• C. 50%
• D. > 50%

Answer 1

The correct option is D > 50%



Above is how the graph will shift if the accelerating potential is increased. I am sure you guys would have guessed the same as it's pretty obvious that if you increase the accelerating potential then the maximum energy of the electrons increases thereby increasing the maximum energy (or decreasing the cut off wavelength) of x ray produced.
Also the graph scales up as now each electron has more energy to lose and can have many more interactions than previous case. This is going to increase the intensity of each wavelength being produced.

Analogy: if you went in a fare with 10 bucks and there was only one ride with that cost then you can only do that ride that too only once. But if you went with 100 then there is also a chance that you may do the 10 buck ride more number of times.

Also notice that in the graph the peak also gets shifted towards left on increasing potential.
See the line in the graph that approximately divides the total number of photons by 50%


So earlier if 50% of the rays were penetrating the given paper now surely I have more rays with higher energy.

Let's say around 60% of the rays are now able to penetrate the paper. Now if I have to bring the number back to 50% then I will have to increase the thickness of the paper. Correct!!!!

Easy right.