A satellite revolves in the geostationary orbit but in a direction east to west. The time interval between its successive passing about a point on the equator is:

Explanation

To solve the problem of finding the time interval between successive passes of a geostationary satellite moving in the direction east to west, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Geostationary Orbit**:
A geostationary satellite orbits the Earth at a height where its orbital period matches the Earth's rotation period. This means it appears to be stationary relative to a point on the Earth's surface.

2. **Determine the Angular Velocity**:
The angular velocity of the Earth (ω_e) is given by:
\[ \omega_e = \frac{2\pi}{T_e} \]
where \(T_e\) is the time period of Earth's rotation, which is 24 hours (or 86400 seconds).

3. **Calculate the Angular Velocity of the Satellite**:
Since the satellite is geostationary, its angular velocity (ω_s) is equal to that of the Earth:
\[ \omega_s = \omega_e \]

4. **Consider the Direction of Motion**:
The satellite is moving in the opposite direction (east to west). Therefore, while the Earth rotates eastward, the satellite's effective angular velocity concerning a point on the equator will be:
\[ \omega_{relative} = \omega_e - \omega_s = 0 - \omega_e = -\omega_e \]

5. **Determine the Time Interval for One Complete Pass**:
The time interval (T) for the satellite to pass a point on the equator can be calculated using:
\[ T = \frac{2\pi}{|\omega_{relative}|} \]
Since \(|\omega_{relative}| = \omega_e\):
\[ T = \frac{2\pi}{\omega_e} \]

6. **Substituting the Value of Angular Velocity**:
We know that:
\[ \omega_e = \frac{2\pi}{T_e} \quad \text{where } T_e = 86400 \text{ seconds} \]
Thus:
\[ T = \frac{2\pi}{\frac{2\pi}{T_e}} = T_e = 86400 \text{ seconds} \]

7. **Calculating the Time Interval**:
Since the satellite is moving in the opposite direction, the time interval between successive passes is:
\[ T_{interval} = \frac{T_e}{2} = \frac{86400}{2} = 43200 \text{ seconds} = 12 \text{ hours} \]

### Final Answer:
The time interval between successive passes of the satellite about a point on the equator is **12 hours**.