Why India awarded five penalty runs? What is obstructing the field rule?

Team India were awarded an additional 5 runs during the 2nd session of the 1st Test against England at Headingley as England were penalised for the ball hitting the helmet placed on the ground alongside the wicketkeeper. When the wicketkeeper couldn't catch the ball coming to his left, his dive ultimately directed the ball towards the helmet.  Stokes was visibly upset when the umpire rightly awarded the extra 5 runs to India, who had a brilliant 2nd session featuring Yashasvi Jaiswal's 5th Test hundred as well. 

  What does the rule say? 

When fielders aren’t wearing their protective helmets, they can only place them on the ground directly behind the wicket-keeper and in line with the stumps at both ends. They cannot be left lying around elsewhere on the field.

 

• If a live ball hits a helmet that’s placed legally (as described above), the ball becomes dead immediately. Then:
• If it was a no ball or a wide, the umpire will signal that as usual.
• The batting team will also be awarded 5 penalty runs.

Check ENG vs IND 1st Test Day 1 LIVE SCORE UPDATES here  Jaiswal-Gill rebuilding India's innings after lunch 

India got off to a strong start, putting up a 91-run opening stand before KL Rahul was dismissed for 42 by Brydon Carse and debutant Sai Sudharsan fell for a duck to Ben Stokes just before lunch. The visitors headed into the break at 92 for 2.

The second session, however, belonged entirely to India. Yashasvi Jaiswal (unbeaten on 100) and captain Shubman Gill (not out on 58) stitched together a dominant partnership, adding 123 runs without losing a wicket and placing India in a commanding position early in the Test.