In Newtonian gravitation, light is not considered to have mass, but it is still affected by gravity. According to Newton's theory of gravity, any object with mass, including celestial bodies like the Sun, creates a gravitational field that affects the motion of other objects in its vicinity.
In the case of light, although it doesn't have mass, it still carries energy and momentum. According to Newtonian physics, any particle or wave with energy and momentum will experience a gravitational force in the presence of a gravitational field. As light passes through a gravitational field, it follows a curved path due to the influence of gravity.
During a solar eclipse experiment, when light from distant stars passes close to the Sun, the Sun's gravitational field bends the path of the light. This bending of light is known as gravitational lensing. Since the Sun is much more massive than the Earth, its gravitational field is significant enough to cause a measurable deflection of starlight passing near it.
Therefore, even though Newtonian gravitation doesn't explicitly consider the masslessness of light, it still predicts the deflection of light by gravity because it accounts for the influence of gravity on energy and momentum, which light possesses. However, it's important to note that the magnitude of the predicted deflection in Newtonian gravitation is significantly smaller compared to the predictions of Einstein's general theory of relativity, which provides a more accurate description of gravitational effects.