Question

The range for unit step function for u(t – a), is ________

(a) t < a

(b) t ≤ a

(c) t = a

(d) t ≥ a

I got this question during an internship interview.

My doubt stems from Useful Signals topic in section Signals and Systems Basics of Signals and Systems

Answer 1

Right choice is (d) t ≥ a

Easiest explanation: A unit step signal u(t) = 1 when t ≥ 0 and 0 when t < 0

∴ u(t – a) = 1 when t – a ≥ 0 ⇒ t ≥