Newcastle University is to close its pure physics courses because of a lack of funds and falling numbers of applications from students.
There are warnings that more courses could close
The Institute of Physics said the decision was regrettable.
It is calling on the government to review the way it funds university science courses.
The announcement comes days after Exeter University announced it was closing its chemistry department.
Education Secretary Charles Clarke has drawn up a list of subjects of national importance - including the sciences - and is asking the Higher Education Funding Council for England (Hefce) to investigate whether more should be done to protect them.
The 30 students who started Newcastle's pure physics courses - BSc and MPhys - this year will be the last to do so.
However, the university will continue - and may even expand - its applied physics courses it says.
A statement said: "Consideration is now being given to expanding areas of applied and interdisciplinary physics, such as nanotechnology and materials sciences, which
are generally regarded as more attractive to students and have greater potential for generating research income."
The head of Newcastle's faculty of science, Professor Malcolm Young, said: "It is essential that we move with the times in the sciences and I am delighted at the progress we are making," he said.
"I believe we will emerge with a much stronger portfolio of physics and
chemistry teaching and research programmes which will be recognised as being
more relevant to the world we live in today."
Physics at Newcastle scored a 4 in the 2001 research assessment exercise (RAE), which determines how much money departments get.
But the bulk of research funding goes to departments around the country rated
as 5 or 5*.
However, nanotechnology was "flagged" as a 5-star subject within physics in the RAE.
A spokesman for the Institute of Physics, Professor Peter Main, said Newcastle's decision was "regrettable".
He said a third of the UK's physics departments had closed in the past 10 or 12 years and more might follow.
"There are several others that are close to the edge, " he told BBC News.
He said the funding of physics courses didn't take account of the higher teaching and equipment costs required and should be reviewed.
A government spokesman said funding for higher education had increased and that next year it would be spending £2bn more than three years ago.
"We have also targeted extra resources specifically for science and research. By 2007-08 we will be spending over £5bn in this area up from £3.9bn in 2004-05," he said.
"This proves that this government is committed to science and research but at the end of the day, departmental closures are a matter for universities themselves. By law we cannot tell a university which course to run.
"Separately, we have created a list of subjects of strategic national importance. The sciences are on that list. We have asked Hefce to consider the list and report back on whether any of the subjects need protecting further and if so how we could work with the sector to protect them."