We all know that light travels in a straight line. So whenever light passes over a Black Hole, the massless photon particles fall into the event horizon of a Black Hole. Here actually gravity does not act on the massless photons but they themselves, while travelling in a line, fall straight into the event horizon, which we misunderstand as "Gravity has attracted massless photons". Photons are not attracted by Gravity of Black Hole.

Hope it helps!

You can watch this video of Vigyan Tv India

https://youtu.be/Vz6qJtJ5RZQ

In this video, your doubt is very simply explained...

Thank you!

We all know that light travels in a straight line. So whenever light passes over a Black Hole, the massless photon particles fall into the event horizon of a Black Hole. Here actually gravity does not act on the massless photons but they themselves, while travelling in a line, fall straight into the event horizon, which we misunderstand as "Gravity has attracted massless photons". Photons are not attracted by Gravity of Black Hole.

Hope it helps!

You can watch this video of Vigyan Tv India

Vigyan Tv India video link (https://youtu.be/Vz6qJtJ5RZQ)

In this video, your doubt is very simply explained...

Also another reason for the question can be as followed:

According to famous Einstein's theory of relativity , as an object travels with a very high speed , its mass increases!!! And we know, photons travel with a flashy speed of 30,00,00,000 m/s (i.e 3 Lakh Km/second..!!!) . So photons do possess some mass when they are in motion! And due to that black hole pulls photons towards itself and doesn't allow them to go beyond.

Thank You!

Hello Mahesh,

This is an explanation given by Stephen Hawkings -

A black hole has a boundary, called the event horizon. It is where gravity is just strong enough to drag the light back and prevent it from escaping. Because nothing can travel faster than light, everything else will get dragged back also. 

Hope this helps.