Imagine a particle of mass m, constrained to move along the x-axis, subject to some specified force F(x, t). The program of classical mechanics is to deter- mine the position of the particle at any given time: x(t). Once we know that, we can figure out the velocity (\( v=\frac{dx}{dt}\) ), the momentum (p = mv), the kinetic energy ( \( T=\frac{1}{2}mv^2 \) ), or any other dynamical variable of interest. And how do we go about determining x(t)? We apply Newton's second law: F = ma. (For conservative systems the only kind we shall consider, and, fortunately, the only kind that occur at the microscopic level---the force can be expressed as the derivative of a potential energy function, \( F=-\frac{\partial V}{\partial x} \) , and Newton's law reads \( m\frac{d^2x}{dt^2}=-\frac{\partial V}{\partial x} \) .) This, together with appropriate initial conditions (typically the position and velocity at t 0), determines x(t). Quantum mechanics approaches this same problem quite differentl...
Mikroskop elektron adalah instrumen, yang menggunakan elektron untuk menghasilkan gambar dari spesimen yang diperiksa. Baca lebih lanjut di sini. Prototipe dari mikroskop elektron pertama ditemukan oleh Max Knoll dan Ernst Ruska, yang insinyur Jerman, pada tahun 1931. Itu adalah penemuan dan ide-ide dari Louis de Broglie, seorang ahli fisika Perancis, bahwa itu didasarkan pada.