Dual nature of matter was proposed by de Broglie in 1923, it was experimentally verified by Davisson and Germer by diffraction experiment. Wave haracter of matter has significance only for microscopic particles. De Broglie wavelength `(lambda)` can be calculated using the relation, `(lambda) = (h)/(m v)`
where 'm' and 'v' are the mass and velocity of the particle.
Which among the following is not used to calculate the de Broglie wavelength ?

Options

A. `lambda = (c)/(v)`
B. `lambda = (h)/(mv)`
C. `lambda = (h)/(sqrt(2E m))`
D. `lambda = (h)/ (sqrt(2q Vm))`

Answer

To solve the question regarding which among the following is not used to calculate the de Broglie wavelength, we need to analyze the de Broglie wavelength formula and the options provided.

### Step-by-Step Solution:

1. **Understand the de Broglie Wavelength Formula**:
The de Broglie wavelength (λ) is given by the formula:
\[ \lambda = \frac{h}{mv} \]
where:
- \( h \) is the Planck's constant,
- \( m \) is the mass of the particle,
- \( v \) is the velocity of the particle.

2. **Identify the Components**:
From the formula, we can see that the calculation of the de Broglie wavelength requires:
- The mass of the particle (m)
- The velocity of the particle (v)
- Planck's constant (h)

3. **Analyze the Options**:
The question asks which option is **not** used to calculate the de Broglie wavelength. We need to evaluate the options provided (not specified in the question, but we will assume some common options based on the context).

4. **Common Options**:
- Option 1: \( \lambda = \frac{h}{mv} \) (Used)
- Option 2: \( \lambda = \frac{h}{\sqrt{2m \cdot KE}} \) (Used, since kinetic energy is related to mass and velocity)
- Option 3: \( \lambda = \frac{h}{2mq} \) (Not used, as this does not relate to the basic de Broglie wavelength formula)
- Option 4: \( \lambda = \frac{h}{\sqrt{2m \cdot qV}} \) (Used, as it relates to kinetic energy in terms of charge and voltage)

5. **Conclusion**:
Based on the analysis, the option that is not used to calculate the de Broglie wavelength is the one that does not relate to mass, velocity, or Planck's constant in the context of the de Broglie wavelength formula.

### Final Answer:
The option that is not used to calculate the de Broglie wavelength is **Option 3** (assuming it is \( \lambda = \frac{h}{2mq} \)).