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# Light and Matter
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- $\Delta E = hf = {hc \over \lambda}$ between ground / excited state
-- $E$ and $f$ of photon: $E_2 - E_1 = hf = hc$
+- $E$ and $f$ of photon: $E_2 - E_1 = hf = {hc \over \lambda}$
- Ionisation energy - min $E$ required to remove e-
- EMR is absorbed/emitted when $E_{\operatorname{K-in}}=\Delta E_{\operatorname{shells}}$ (i.e. $\lambda = {hc \over \Delta E_{\operatorname{shells}}}$)
$${dV \over dt} = {\operatorname{change in volume} \over \operatorname{respect to time}}$$
-**position $x$** - distance from origin or fixed point
-**displacement $s$** - change in position from starting point (vector)
-**velocity $v$** - change in position with respect to time
-**acceleration $a$** - change in velocity
-**speed** - magnitude of velocity
+**position $x$** - distance from origin or fixed point
+**displacement $s$** - change in position from starting point (vector)
+**velocity $v$** - change in position with respect to time
+**acceleration $a$** - change in velocity
+**speed** - magnitude of velocity
$$v_{\operatorname{avg}}={\Delta x \over \Delta t}={{x_2 - x_1} \over {t_2 - t_1}}$$
$$\operatorname{speed}_{\operatorname{avg}}={\Delta v \over \Delta t}$$
| $v=u+at$ | $s$ |
| $s=ut + {1 \over 2} at^2$ | $v$ |
| $v^2 = u^2 + 2as$ | $t$ |
-| $s= {1 \over 2}(u+v)t$ | $a$ |
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+| $s= {1 \over 2}(u+v)t$ | $a$ |
+
+## Velocity-time graphs
+
+- area = displacement
+
+## Definite integrals
+
+$$\int_a^b f(x) \cdot dx = [F(x)]_a^b=F(b)-F(a)$$
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