An oscilloscope displays a measured rise time of 10 ns when observing a fast pulse. If the oscilloscope itself has a specified rise time of 6 ns, then what is the approximate actual rise time of the signal being measured?

• A4 ns
• B8 ns
• C6 ns
• D12 ns

Answer & step-by-step solution

Correct answer: B. 8 ns

Quick explanation

Rise times combine by root-sum-square, so t_signal = √(10² − 6²) = √64 = 8 ns.

t_measured² ≈ t_signal² + t_scope² t_signal = √(10² − 6²) = 8 ns

Exam tipNever subtract rise times directly; use root-sum-square.