Soviet authorities seeking to strengthen charges against dissident spokesman Anatoly Scharansky questioned ostracized scientist Benjamin Levich for seven hours today on his relations with the jailed human-rights activist.

Levich, 60, a physicist, said he had told authorities that he knows Scharansky and is convicted that Scharansky has done nothing unlawful. A spokesman for the small group of dissidents publicly active in Moscow, Levich said he acknowledged that he and Scharansky had signed some letters together but said he had refused to answer other questions about Scharansky.

Scharansky, a 29-year-old computer specialist who had been refused permission to emigrate to Israel, was arrested March 15 after the Soviet press charged that he worked for the Central Intelligence Agency.

Last month, Los Angeles Times reporters Robert C. Toth, who had had Scharansky's help in preparing articles about Soviet science, was arrested by the KGB secret police and questioned about his contacts with Scharansky. Last week, the Kremlin said Toth was also a spy for the CIA.Toth has denied the charge. He was released and has left the Soviet Union.

Scharansky, a spokesman for a dissident group founded last year to monitor Soviet compliance with the human-rights guarantees of the Helsinki accords on European security, reportedly faces a treason charge and could be sentenced to death.

Levich has been ostracized socially and professionally since applying to emigrate to Israel more than five years ago. He lost his positions as professor and department head of Moscow State University.

Last week, several hundred scientists gathered at Oxford University in England to honor Levich at a symposium on hydrodynamics, in which he is a pioneer. Forty signed a telegram to Soviet leader Leonid Brezhnev asking that Levich be allowed to emigrate.