Republican presidential hopeful Howard Baker has decided to capitalize on the fervor over the Iranian crisis with a television commercial featuring a dramatic confrontation between the Tennessee senator and an indignant Iranian student.

Baker, the Senate minority leader, outshouts the student in the spontaneous incident, filmed this month at the University of Iowa.

The unidentified student hurls a series of verbal accusations demanding to know why the senator isn't more interested in the plight of the Iranian people.

Baker dramatically points a finger at the student and declares to loud applause: "Because I'm concerned about 50 Americans" -- the hostages at the U.S. embassy in Tehran.

As the scene fades out, Baker adds: "The America you once trusted is back. The American you once feared to cross is back. The American that cherishes peace but will fight for freedom is back. And in our generation it's back to stay."

The ad is one of the strongest statements to date on Iran by any of the Democratic and Republican presidential candidates, who have shown a remarkable restraint in criticizing President Carter's handling of the crisis.

Previously, Sen. Edward Kennedy, Carter's chief rival for the Democratic nomination, has criticized the president for allowing the shah of Iran to enter the country for hospital treatment. And Republican John Connally has attacked Carter for not briefing major opponents on the Iranian situation. "We're operating out of an abundance of ignorance," Connally has said.

The Baker campaign has purchased $36,000 worth of television time in five Iowa cities to show the film over the next three weeks. Iowa's Jan. 21 precinct caucuses will be the first formal test of the various presidential hopefuls.

In the ad, Baker proposes creating a 50,000-man "First Brigade" of troops trained in anti-terrorist tactics, because "this must never happen again in our lifetime" -- a reference to the seizure of hostages.

The commercial was made by the respected political advertising firm of Bailey, Deardourff and Associates, which is handling Baker's campaign.

"There's a mood out there (in the nation) that is really different. I don't mean it's a militant mood," Douglas Bailey of the advertising agency said yesterday. "It's anger, but it's also a feeling that we as citizens haven't done right by our country."

The commercial is designed to captalize on the mood.