Writing a "visualization"

[RockmanX3]

There are several parts in a script I'm writing that involve "visualizations" like when the characters are talking and I want to insert footage of what they're talking about when the movie is playing. For example...

Note: Not verbatim from my actual script since I haven't written these parts yet.

BOB
"What if we decided to nuke a country out of the blue?"

CUT TO:

EXT. SOMEPLACE WHERE A NUCLEAR EXPLOSION IS HAPPENING, BLAH BLAH BLAH

A nuclear bomb goes off, displaying a huge mushroom cloud from the sky.

BOB (V.O.)
"That would be pretty devastating."

CUT TO:

INT. BOB'S HOUSE - DAY

I was thinking that "Bob" would be talking, then I would insert some stock footage of a nuclear explosion, then cut back to "Bob" talking. What would be the best way to write in a visualization?