< 07-Ray_Op... Final Review 5 08-Image_... * ধে NYC-Fin... WORKSHEET رف T + 09-Quantu... PHY-NYC Problem 9: Hydrogen emits visible light at specific wavelengths. The wavelengths are traditionally named as follows: Ha = 656.3 nm (red), H8 = 486.1 nm (cyan), Hy = 434.1 nm (blue), Hs = 410.2 nm (violet). Light from hydrogen passes through a diffraction grating creating an emission spectrum of fringes. a) If the second-order Ha line is observed at 41.018°, what is the number of lines per millimetre of the grating? b) What is the angular separation of the Hy and Hs lines in the 1st order? [Keep at least 3 decimal places in your work.] c) How many complete orders are visible on one side of the centre of the spectrum? Problem 10: In a photoelectric-effect experiment, light shines on an aluminum cathode. You are told the work function of aluminum is 6.85 x 10-19 J. a) If electrons emerge from the aluminum surface with a maximum kinetic energy of 1.30 eV. What is the wavelength of the light? b) Find the cut-off frequency for aluminum. c) Later in that experiment, the wavelength of light shining on the aluminum cathode is decreased from 240 nm to 210 nm. What is the change in the stopping potential? Problem 11: A by-product of some nuclear power reactors is the isotope 239Pu. This isotope has a half-life of 24 120 years and decays by alpha emission: 239Pu 235U + a. Suppose a sample of this plutonium isotope has a mass of 0.7939109 kg at t = 0. a) How many atoms are initially in the sample? b) What is the initial activity of the sample in Becquerels? c) How many years does it take for the activity to decrease to 0.100 Bq? [Use the conversion factor: 1 year = 365.25 days.] d) What is the total energy released between t = 0 and the time found in part (c)? [Use the masses: mpu = 239.052157 u, mu= 235.043924 u, ma = 4.002602 u]

< 07-Ray_Op... Final Review 5 08-Image_... * ধে NYC-Fin... WORKSHEET رف T + 09-Quantu... PHY-NYC Problem 9: Hydrogen emits visible light at specific wavelengths. The wavelengths are traditionally named as follows: Ha = 656.3 nm (red), H8 = 486.1 nm (cyan), Hy = 434.1 nm (blue), Hs = 410.2 nm (violet). Light from hydrogen passes through a diffraction grating creating an emission spectrum of fringes. a) If the second-order Ha line is observed at 41.018°, what is the number of lines per millimetre of the grating? b) What is the angular separation of the Hy and Hs lines in the 1st order? [Keep at least 3 decimal places in your work.] c) How many complete orders are visible on one side of the centre of the spectrum? Problem 10: In a photoelectric-effect experiment, light shines on an aluminum cathode. You are told the work function of aluminum is 6.85 x 10-19 J. a) If electrons emerge from the aluminum surface with a maximum kinetic energy of 1.30 eV. What is the wavelength of the light? b) Find the cut-off frequency for aluminum. c) Later in that experiment, the wavelength of light shining on the aluminum cathode is decreased from 240 nm to 210 nm. What is the change in the stopping potential? Problem 11: A by-product of some nuclear power reactors is the isotope 239Pu. This isotope has a half-life of 24 120 years and decays by alpha emission: 239Pu 235U + a. Suppose a sample of this plutonium isotope has a mass of 0.7939109 kg at t = 0. a) How many atoms are initially in the sample? b) What is the initial activity of the sample in Becquerels? c) How many years does it take for the activity to decrease to 0.100 Bq? [Use the conversion factor: 1 year = 365.25 days.] d) What is the total energy released between t = 0 and the time found in part (c)? [Use the masses: mpu = 239.052157 u, mu= 235.043924 u, ma = 4.002602 u]