Statement-1 : In an e.m. wave magnitude of magnetic field vector `vec B` is much smaller than the magnitude of vector `vecE`
Statement-2 : this is because in and e.m. wave `E//B=c=3xx10^(8) m//s`.

Options

A. Statement-1 is true, statement-2, is true, statement-2 is a correct explanation for statement -1
B. statement -1 is true, statement -2 is true, statement -2 is NOT a correct explanation for statement -1
C. statement-1 is true , statement-2 is false
D. statement-1 is false, statement-2 is true

Answer

To analyze the statements provided in the question, we will break down the concepts related to electromagnetic (e.m.) waves and the relationship between the electric field (E) and magnetic field (B) vectors.

### Step-by-Step Solution:

1. **Understanding Electromagnetic Waves**:
Electromagnetic waves consist of oscillating electric and magnetic fields that are perpendicular to each other and to the direction of wave propagation.

2. **Magnitude Relationship**:
In an electromagnetic wave, the relationship between the magnitudes of the electric field (E) and the magnetic field (B) is given by the equation:
\[ \frac{E}{B} = c \]
where \( c \) is the speed of light in a vacuum, approximately \( 3 \times 10^8 \, \text{m/s} \).

3. **Implication of the Relationship**:
From the equation \( E = cB \), we can infer that the electric field strength is much greater than the magnetic field strength because \( c \) is a very large number. This implies:
\[ E \gg B \]
Thus, the magnitude of the magnetic field vector \( \vec{B} \) is much smaller than the magnitude of the electric field vector \( \vec{E} \).

4. **Energy Density in Electromagnetic Fields**:
The energy density (energy per unit volume) associated with the electric field \( U_E \) and magnetic field \( U_B \) can be expressed as:
\[ U_E = \frac{1}{2} \epsilon_0 E^2 \]
\[ U_B = \frac{1}{2} \frac{B^2}{\mu_0} \]
In a given volume, the energy densities of the electric and magnetic fields are equal, leading to the conclusion that:
\[ U_E = U_B \]

5. **Equating Energy Densities**:
By equating the energy densities, we can derive:
\[ \frac{1}{2} \epsilon_0 E^2 = \frac{1}{2} \frac{B^2}{\mu_0} \]
Simplifying this gives:
\[ \epsilon_0 E^2 = \frac{B^2}{\mu_0} \]
Rearranging yields:
\[ \frac{E^2}{B^2} = \frac{1}{\epsilon_0 \mu_0} \]
Since \( \frac{1}{\epsilon_0 \mu_0} = c^2 \), we have:
\[ \frac{E}{B} = c \]

6. **Conclusion**:
Therefore, both Statement-1 and Statement-2 are true. However, Statement-2 does not provide a correct explanation for Statement-1. The reason is that while it correctly states the relationship \( E/B = c \), it does not explain why the magnitudes differ.

### Final Answer:
- **Statement-1**: True
- **Statement-2**: True, but not a correct explanation of Statement-1.