The decline bench press gives you have a limited range of motion. You can use more weight because of both mechanical advantage and less total work being performed. By only bringing the bar down to your lower chest, you severely limit the distance you move the bar.
The time difference that you sense is due to the way sound and light travel. Light travels extremely fast (300,000,000 m/s). In fact, it is faster than anything else. Sound travels at a measly 343 m/s through air. Therefore we can see light in an instant, but it takes a while to hear thunder. Sound has another disadvantage because it tends to bounce off molecules in the air. This makes the sound travel in all different directions.
Nature of Light. Light is a wave, but the traveling disturbance is and electric and magnetic field, not a pressure variation like a sound wave. Sound has to travel through matter, but light does not have to travel through a medium. Therefore light can travel through a vacuum. Light waves also carry energy with them; that is how sunlight warms us up when we absorb it. In a vacuum, light travels with a speed of about 3Â´108 m/s, or 300,000,000m/s, i.e. very fast.