Question

magnesium ribbon burns with sparkling light

Answer 1

it is highly reactive so it reacts vigorously with fire to birn with sparkilng light

Answer 2

Magnesium ribbon burns with a sparkling white light due to the reaction with oxygen present in the air. 

The bright light results because this reaction produces a lot of heat. When the magnesium gets really hot, it emits energy in the form of light (heat is also how the sun produces light).