Question: In what particular situation you will need a depth knowledge of math/physics in software engineering?

Answer: 
Good knowledge of Mathematics is highly recommended [not mandatory]. Physics in my opinion is not that crucial to know but basic physics knowledge will surely help.

Computer science is rooted to Maths and both programming and mathematics require good analytical and problem solving skills.
The question asked about 'Software Engineering' specifically, and, of course, Software Engineering can include somewhat more than programming. As a software engineer you'll need to do things like estimate the effort required to do a project, or estimate the impact of risks. Risk mitigation and some effort-estimation models are based on probability distributions that are not trivial, and, to be used as intended, must be understood.

Magnitude estimations are another area. If you are designing an algorithm that can potentially be used many times or need to handle large amounts of data, then you will want to evaluate how the time required for a candidate algorithm will grow when it's required to execute many times or with increasing data loads, versus some other algorithm that may be more or less efficient. That requires a math model of your algorithms.

My advice: if you plan to be involved in some of the larger aspects of software development, don't bypass the math courses.