Chapter 30: Quantum Physics Selected Solutions

Selected Solutions

7. (a) Since , the halogen bulb has the higher peak frequency.

(b) Since , the standard incandescent bulb has the longer peak wavelength.

The halogen bulb produces a peak frequency closer to 5.5 x 10¹⁴ Hz than the standard incandescent bulb.

21. (a) The power of the bulb, P gives the amount of energy per second while the energy per photon is given by hc/l. Therefore, the ratio lP/hc equals the number of photons per second.

So, . The red bulb emits more photons per second than the blue bulb.

(b)

So, E_red < E_blue. The blue bulb emits photons of higher energy than the red bulb.

(c) Red bulb

Blue bulb

41. For elastic scattering, the kinetic energy is conserved. So, the kinetic energy of the recoiling electron equals the kinetic energy lost by the X-ray photon.

KE_electron = -DKE_photon = K_i - K_f = 36 keV - 27 kleV = 9 keV

57. (a)

Since and m_e < m_p, for identical de Broglie wavelengths, an electron has a greater kinetic energy than a proton.

(b)

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