【正文】 gases is bombarded by photons (light), electrons in the substance will absorb the energy of photons and they will be emitted, one electron could only absorb the energy of one photon. It is usually a way to find the Planck constant. As the limiting of the facilities, the main results which include the wavelength of lights and the planck constant are not easy to be gotten in accurate values. This lab was designed to find the Planck constant based on the light diffraction and the photoelectric effect, there are four aims of this experiment which are building a spectrometer, finding wavelengths for lasers and LEDS and finding the Planck constant. TheoremWhen a beam of monochromatic light passing through a diffraction grating, the wavelength and the distance from the grating to the center fringe follow the two relationships: amp。liquidsDiffraction and the photoelectric effectIntroductionThe Planck constant is a constant of physics which reflects the magnitude of energy quantum in the field of quantum mechanics. The sign of Planck constant isand it is named by Max Planck in 1990. The proportionality constant between a photon’s energy and the frequency of its electromagnetic wave was the first definition of the Planck constant. This theory was generalized by Louis de Broglie in 1923 and confirmed by experiments. There is a difference between and (bar). is called theDirac constant or reduced Planck constant which is equal to the Planck constant divided by 2π. (1)The photoelectric effect is the effect that when a matter which can be metals, nonmetallic solids,or . For the relationships, is the order of fringes and it is equal to , is the wavelength of this light, , , are the distance from the grating to the center fringe, the fringes to the center fringe and the distance between two slits in the grating respectively, is the angle between the center line and the line connected by the fringe center and the slit. The formula of the photoelectric effect is, is the energy of the electro escaping from the object, is the frequency of the light which shots at the surface of the object, is the Planck constant and is the work function. For a certain object, the work function is a constant. For LED, This formula also can be rewritten as where is the quantity of electric charge and it is and is the voltage of the LED. For EM wave, (C is the speed of light and is its frequency.Formula:, , , , .AimsAim I: building a spectrometerl Apparatus: carton, circular diffraction grating, a piece of paper, ruler, white light LED, scissors. Diagram 1 is the simple model the spectrometerl Diagram 1: simple model of the spectrometerl MethodsThe process of making a simple spectrometer was mainly 5 steps and operated by two people. First of all, a hole with proper sizes in the front of the carton was removed by the scissors. Secondly, a circular diffraction grating was set to the hole to cover it, which was used to produce the diffraction pattern. Thirdly, a piece of paper was fixed at the internal back surface of the carton, which was served as a screen to bring out the diffraction pattern. Then, at a proper position on the top surface, an elliptic hole which was long and narrow (this is to help to view because the light from THE LED is not be very strong) was removed to view the diffraction pattern which was inside the carton. Next, a ruler was put at the bottom near to the back surface and the purpose of this step was measuring the distance between different fringes. The experiment started after the spectrometer was finished. At the first, the light of the torch was shot to the center of the diffraction grating vertically and the diffraction pattern appeared on the screen. Then, observing the diffraction pattern through the viewing hole in top and record the position of each fringe. Next, the distances from the center to each fringe were read from the ruler and they are recorded on the drafter paper. Later, the length (L) between the f