You've heard of foreigners buying up the homes in Beverly Hills and the banks and the stock of steel and auto companies, but one less noticed foreign invasion is in American science education.

The United States produces only about 1,000 PhD physicists every year, and about 320 of those are foreigners. In engineering, foreigners make up more than 33 percent of the PhD graduates.

Although three-quarters of the foreigners will take the degrees and go home, the number who stay here to get full-time jobs is growing and the total is between 5 and 10 percent higher than it was a decade ago.

The influx of foreign students into graduate science studies in America has two chief causes -- first, more foreigners can afford to send children here to get an education. The American dollar is worth less, and they have more of their currency to trade for dollars.

Second, American students have been turning away from some basic sciences, studying at the graduate level especially, for the past decade. Because of this, shortages of students have developed and chairmen of physics departments have filled the gapswith foreigners, according to Susanne Ellis, statistician for the American Institute of Physics.

Thus, some statisticians feel, the United States may face a shortage of scientists in physics and chemistry both in basic research and in industry in the next decade.

The number of graduate physics students has dropped in 10 years from 15,000 to 10,000 per year, according to Ellis.

In chemistry, the number of students in graduate school has dropped about 20 percent, from 2,200 a decade ago to 1,540 this year, according to Robert Newman of the American Chemical Society.

Students began to turn away from physics and chemistry in 1970, when economic conditions forced cuts in research funds, and when space and nuclear research programs began to narrow. The number of jobs in universities stopped growing, and science and engineering jobs available in industry dropped to the lowest mark since Deutsch, Shea and Evans Inc. began keeping an index in 1961.

Through the 1960s, the demand for Physicists exceeded the American supply, and the United States important physicists from other countries and other disciplines, according to Lee Grodzins, an MIT specialist in science manpower.

"The situation changed dramatically around 1970 as the number of longterm physics openings vanished. The older physicists who were looking for positions found few available, and large numbers lift the field; the younger physicists embarked on alternate careers rather than face the uncertain prospects" of merely temporary appointments, Grodzins said.

After 1970, the demand for scientists in industry bounced back, the Deutch index has climbed steadily since 1971 to last year, when it reached 144. The academic demand did not come back so readily, but is apparently improving again, Ellis said.

In the absence of Americans to fill the demand, foreigners increasingly have done so.

The decline in physics and chemistry graduate students has occurred at the same time the college population grew, and when students were flooding undergraduate courses in the applied sciences, such as four-year engineering courses and chemical engineering.

Last year, those with bachelor's degrees in chemical engineering drew an average starting salary of about $20,000, while physics students with a bachelor's degree earned an average of $2,000 to $4,000 less.

Physics students have traditionally sought academic research jobs, avoiding industrial work to the point that physics departments discouraged applied work. The graduate study handbook at the University of Maryland reportedly states that "research that is entirely applied or developmental is not acceptable."

A major change has occurred in physics education, says Grodzins of MT. "From now on the demand for physicists will be closely coupled to funding by government sources and by industrial research and development laboratories. We may predict with some certainty that throughout this century, the supply of physicists will always be out of balance with the components of demand."

Now there is greater demand in industry, and the universities have suffered, Grodzins said. "The faculities of physics are aging, becoming almost completely tenure, with too few in junion ranks and too few opportunities for young scientists. Physics academe has become so weakened by the events of the past decade that the continued vitality of the the departments must be a prinicipal concern."