Which of the following statements is/are INCORRECT :

Options

A. All spectral lines belonging to Balmer series in hydrogen spectrum lie in visible region
B. if a light of frequency v falls on a metal surface having work function hv, photoelectric effect will take place only if `v le v_0`
C. The number of photoelectrons ejected from a metal surface in photoelectric effect depends upon the intensity of incident radiations.
D. The series limit wavelength of Balmer series for H-atom is `4/R`, where R is Rydberg's constant.

Explanation

To determine which of the statements is/are incorrect, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement A**: "All these spectral lines belonging to the Balmer series in hydrogen spectrum lie in the visible region."
- The Balmer series corresponds to transitions where the electron falls to the n=2 energy level from higher levels (n=3, 4, 5, ...). The wavelengths of these transitions fall within the visible spectrum (approximately 400 nm to 700 nm).
- **Conclusion**: This statement is **correct**.

2. **Statement B**: "If a light of frequency μ falls over the metal surface having the function hν, the photoelectric effect will take place only if μ is less than or equal to ν₀."
- The photoelectric effect occurs when the frequency of the incident light (μ) is greater than or equal to the threshold frequency (ν₀) of the metal. The kinetic energy of the emitted photoelectrons is given by the equation KE = hμ - hν₀. For photoelectrons to be emitted, KE must be greater than or equal to zero, which implies μ must be greater than or equal to ν₀.
- **Conclusion**: This statement is **incorrect**.

3. **Statement C**: "The number of photoelectrons ejected from the metal surface in the photoelectric effect depends upon the intensity of the incident radiation."
- The intensity of the incident radiation is related to the number of photons striking the surface. A higher intensity means more photons, which can lead to more photoelectrons being emitted, assuming the frequency is above the threshold.
- **Conclusion**: This statement is **correct**.

4. **Statement D**: "The series limit wavelength of the Balmer series for hydrogen atom is λ = 4/R, where R is the Rydberg constant."
- The series limit for the Balmer series corresponds to the transition from n=2 to n=∞. Using the Rydberg formula, we can calculate the wavelength at this limit: 1/λ = R(1/2² - 1/∞²) = R(1/4). Therefore, λ = 4/R.
- **Conclusion**: This statement is **correct**.

### Final Conclusion:
The only incorrect statement is **B**.