PHYS212 Project Video | Alperen Uğur Erden

Added: 2026-05-12

[00:00:00]Hi, I am Alperen. This is our physics project in the semester 212 physics project. Actually, we measure the most fundamental things in the physics applying constant. With the four equipment actually, LEDs, power supply, of course, and diffraction grating and a webcam. That's all. I just want to announce our results in the beginning of the video with the paper, [snorts] of course.

[00:00:31]Our final value is the 7.00 * 10 to the minus 34 joule seconds. The accepted value is the 6.626.

[00:00:42]So, we are the within the 5 5.7%.

[00:00:46]It's actually accurate results for the in the school equipments. You can see our graph in there.

[00:00:57]The idea is the coming from this one of the greatest physicists in the world, the Albert Einstein. And the photon of the light. The photon carries an energy equals to h times its frequency.

[00:01:13]Um When you slowly raise the voltage on the LEDs, at some threshold value, the lights glow.

[00:01:25]At this point, the electrical energy is converted into the one photon. This gives us a simple linear equation. V V0 equals AC over A times A times 1 over lambda.

[00:01:41]So, if you measure the threshold voltage for the several LEDs of different colors and plot and plot V0 against 1 over lambda, we get straight line.

[00:01:56]The slope of that line multiplied by the E over C This is a Planck constant.

[00:02:04]Uh you can see our graph.

[00:02:07]Again.

[00:02:08]Our experiment is has uh two halves. Uh first part is electrical and second part is optical. In this first part, yeah, so in the electrical part, we measure the LEDs uh threshold values. And second part, uh we measure the uh wavelength of the each LEDs from our homemade spectrometer. Then we measure Then we combine the two and read the H from the slope.

[00:02:37]In the electrical part, we try to find uh H slope from the given wavelengths uh its expected value. But after that, we try to find uh wavelength of the lights from our uh homemade spectrometer. Uh actually, we have the three parts in LEDs power supply and resistor. Uh we try to uh find when uh the LEDs glow shine on. And after the LEDs uh shine on, we we we write the voltage value at the time.

[00:03:11]It's the threshold value of the of the LED.

[00:03:14]Actually, you can Actually, you can see the our uh results in the For the wavelength uh in the second part of the our experiment, we built a spectrometer.

[00:03:24]Uh you can see our uh setup. In It is in the shoebox lined with the black paper and a narrow slit cut from the cardstock. Uh you can see a little near stick. It splits uh a thousand a thousand per a thousand per millimeter diffraction grating and Logitech uh webcam.

[00:03:48]Uh In shortly, uh you know, a split. Uh you can see the light behind the the uh paper and it is so small.

[00:04:00]Uh in the that in there there's a grating and uh when you see this light in it is in the zeroth degree.

[00:04:14]And the fraction grating plane is diffract the light in the some points.

[00:04:21]Uh with our Python programs, uh we just measure the distance between them and we try to find uh wavelength of the light uh because uh different wavelengths has different diffraction distance. And because camera and grating slits is very close to the camera, uh simple screen distance formula doesn't work in it or work. So, we let the camera focal length in pixels be number that up so absorb the all geometry.

[00:04:56]Uh We measure it from the red, green, and blue. Uh you can see the our photos at in there.

[00:05:04]Uh there's a three lines.

[00:05:08]Uh first line from uh its light and others from the grating. We measure that points uh distance and we try to find wavelength of the lights.

[00:05:23]Putting all together, uh we plot V0 against the 1/λ uh for for the four LEDs. Uh as a straight line, uh you can see the in the graph.

[00:05:36]Um this slope is 1.310 * 10 ^ -6 m.

[00:05:42]Uh multiplying with the some constants, uh we get the Planck constant equal to 7.00 plus or minus 0.37 with the the experimental error.

[00:05:58]The main remaining limitation is that we measure the light threshold value with our eyes. It can be more accurate from the some technical equipment.

[00:06:10]Found 5.7% above the accepted value. Thank thank you for listening.

[00:06:16]Thank you.