**Photoelectric Effect:**
The photoelectric effect is the phenomenon in which electrons are emitted from a material when it absorbs electromagnetic radiation, such as light. This effect occurs due to the interaction between photons and electrons in the material.

**Current in the Photo Cell Circuit:**
The current in the photo cell circuit is directly proportional to the intensity of light falling on the photo cell. When the same light source is placed at different distances from the photo cell, the intensity of light reaching the photo cell changes. This leads to a change in the current in the circuit.

**Inverse Square Law:**
According to the inverse square law, the intensity of light decreases with the square of the distance from the source. In other words, if the distance from the source is doubled, the intensity of light decreases by a factor of four.

**Calculating the Current at 1m Distance:**
Let's assume the initial intensity of light at a distance of 50 cm is I. According to the inverse square law, when the distance becomes 1 m (100 cm), the intensity of light decreases by a factor of (50/100)^2 = 1/4.

Therefore, the intensity of light at 1 m distance is I/4.

As the current in the circuit is directly proportional to the intensity of light, the current at 1 m distance will also decrease by a factor of 1/4.

Given that the current at 50 cm distance is 40 milliampere, the current at 1 m distance will be:

40 milliampere * (1/4) = 10 milliampere.

Hence, the current in the circuit will be 10 milliampere when the light source is placed at a distance of 1 m from the photo cell.

**Explanation Summary:**
- Photoelectric effect is the emission of electrons from a material when it absorbs light.
- Current in the photo cell circuit depends on the intensity of light falling on it.
- The intensity of light decreases with the square of the distance from the source according to the inverse square law.
- To calculate the current at 1 m distance, we use the fact that the intensity of light decreases by a factor of 1/4 when the distance is doubled.
- Given the initial current at 50 cm distance, we can calculate the current at 1 m distance as 10 milliampere.