equation 10.18. this equation cannot be applied to many-electron atoms. one way to modify it for the more complex atoms is to replace z with ^z 2 σh, where z is the atomic number and σ is a positive dimensionless quantity called the shielding constant. consider the helium atom as an example. the physical significance of σ is that it represents the extent of shielding that the two 1s electrons exert on each other. thus, the quantity ^z 2 σh is appropriately called the effective nuclear charge. calculate the value of σ if the first ionization energy of helium is 3.94 × 10−18 j per atom. ^in your calculations, ignore the minus sign in the given equation. h

Alinearly polarized electromagnetic wave has an average intensity of 196 w/m^2. this wave is directed towards two ideal polarizers (in real polarizers, transmission is also effected by reflection and absorption). polarizer a is oriented with its transmission axis at an angle of θ_1=20.8∘ with the incident electric field. polarizer b has its axis at an angle of θ_2=63.0∘ with the incident electric field. what is the average intensity of the wave after it passes through polarizer a? what is the average intensity of the wave after it passes through polarizer b? suppose that the two polarizers a and b are interchanged. what would the average intensity be after passing through both polarizers?

If the force applied to an object remains constant, is more power needed for the object to move faster ? explain

Aria drove to the store, did some shopping, and then came home. during maria's trip, when was her displacement equal to zero?