Photoelectric Effect — Chemistry perspective
Atomic Structure
9
JEE Qs
8%
Hard
60
min
Master the energy conservation equation (E_photon = Work_Function + KE_electron) and consistently use appropriate units for all quantities.
🧮 Key Formulas
✅ Key Points for JEE
- 1The Photoelectric Effect demonstrates the particle nature of light, where energy is transferred in discrete packets called photons.
- 2Electron emission occurs only if the incident photon's energy (E = hν) is greater than or equal to the work function (Φ) of the metal.
- 3The maximum kinetic energy (KE_max) of the ejected photoelectrons depends linearly on the frequency of the incident light, but is independent of its intensity.
- 4The number of photoelectrons ejected per second is directly proportional to the intensity of the incident radiation, provided the threshold frequency is met.
- 5Work function (Φ) and threshold frequency (ν_0) are characteristic properties of the specific metal surface.
⚠️ Common Mistakes
- ✕Confusing the roles of intensity and frequency: Intensity affects the number of emitted electrons, while frequency (above threshold) determines their kinetic energy.
- ✕Incorrectly applying the energy conservation equation (KE_max = E - Φ) by mixing up incident energy, work function, and kinetic energy terms.
- ✕Using inconsistent units for energy (Joules vs. electron volts) or Planck's constant (h) values (e.g., using J·s when eV·s is more appropriate for a given problem).
📝 Practice Questions
See allQ57.Given below are two statements : Statement (I) : For a given shell, the total number of allowed orbitals is given by n2 . Statement (II) : For any subshell, the spatial orientation of the orbitals is given by −l to +l values including zero. In the light of the above statements, choose the correct answer from the options given below : (1) Both Statement I and Statement II are false (2) Statement I is true but Statement II is false (3) Both Statement I and Statement II are true (4) Statement I is false but Statement II is true
Q57.In a multielectron atom, which of the following orbitals described by three quantum numbers will have same energy in absence of electric and magnetic fields? A. n = 1, l = 0, m1 = 0 B. n = 2, l = 0, m1 = 0 C. n = 2, l = 1, m1 = 1 D. n = 3, l = 2, m1 = 1 E. n = 3, l = 2, m1 = 0 Choose the correct answer from the options given below: (1) B and C Only (2) A and B Only (3) C and D Only (4) D and E Only
Q51.Radius of the first excited state of Helium ion is given as : a0 → radius of first stationary state of hydrogen atom. (1) r = 4a0 (2) r = 2a0 (3) r = a02 (4) r = a04
Q62.Given below are two statements : Statement (I) : A spectral line will be observed for a 2px →2py transition. Statement (II) : 2Px and 2py are degenerate orbitals. In the light of the above statements, choose the correct answer from the options given below : (1) Both Statement I and Statement II are true (2) Statement I is false but Statement II is true (3) Both Statement I and Statement II are false (4) Statement I is true but Statement II is false
Q51.For hydrogen atom, the orbital/s with lowest energy is/are : (A) 4 s (B) 3px (C) 3 dx2−y2 (D) 3 dz2 (E) 4pz Choose the correct answer from the options given below : (1) (B), (C) and (D) only (2) (A) and (E) only (3) (A) only (4) (B) only
Q44.The frequency of revolution of the electron in Bohr's orbit varies with n, the principal quantum number as (1) 1 (2) 1 n4 n2 (3) 1 (4) 1 n n3
NCERT Chapters
- Class 11 Chemistry Ch 2: Structure of Atom
- Class 12 Physics Ch 11: Dual Nature of Radiation and Matter