In lightning , light is seen first and sound is heard later it is due to 1)optical illusion
2) variation in temperature
3) position of observer
4) difference of velocities of light and sound

option 4

Explanation:

Light's velocity in air ( 3 × 10^8 m/s ) is much greater than sound's velocity in air ( 343 m/s )

Hence due to difference in velocities , during lightning light is seen first & sound is heard later

the bal will not change its velocity.

d eras and periods