Light.range

Description

The maximum distance that light travels from a point of emission. This property does not apply to directional lights.

using UnityEngine;

public class Example : MonoBehaviour
{
    // Pulse light's range between original range
    // and half of the original one

    float duration  = 3.0f;
    float originalRange;

    Light lightComponent;

    void Start()
    {
        lightComponent = GetComponent<Light>();
        originalRange = lightComponent.range;
    }

    void Update()
    {
        // Animate between 0 and duration.
        var amplitude = Mathf.PingPong(Time.time, duration);

        // Map from 0..duration to 0.5..1 range.
        amplitude = amplitude / duration * 0.5f + 0.5f;

        // Set light range.
        lightComponent.range = originalRange * amplitude;
    }
}

If the light is an area light, then it has an infinite number of points of emission on it. If the light is not an area light, then the light's position is the single point of emission.