Normally in a home cooking environment you don't notice it, but your oven will lie to you; the temperature on the nice digital display is not the temperature inside of your oven. Once the temperature rises to what you have set it to, the indicator will generally stay on the set value regardless of the actual inside oven temp. Prove this by pre-heating your oven until it "beeps" or indicates it is hot.
Now open the oven door and leave it open. In most every oven the indicator will not change, even though the inside temp is most definitely falling. You will hear the oven cycle on, but the temp indicated won't change.
The original question by Kayeza was asking about temp drop and you are really at the mercy of your oven setting between when the thermostat senses a drop and when it actually turns on the element/burner. This is often adjustable (though by a service person generally) on higher-end ovens and commercial units; unsure but maybe not on cheaper home units.
A consequence to a poorly manufactured or calibrated oven is that it works the opposite way also.. once the thermostat registers enough of a temp drop to cycle on the element, it will heat the oven to a temperature that may be higher than what you have set on the indicator. Again, the display (if digital) will lie to you and show the "350" you set the oven to, even though it may be set to not turn off the element until 10-15 degrees higher. You see this with really cheap home ovens that always seem to scorch food.
As others have suggested, getting a large pizza stone in the oven will help to smooth out the highs and lows of a poorly calibrated oven. Another trick if you know it will take some time to "load" your oven is to preheat it to 50 degrees higher than you need. Once the oven "beeps", open the door and load the oven, then close the door and reduce the temp to where it should be. The drop in temp of the oven then will still leave it near the ideal temp you are looking for. Works great for getting a good "oven spring" for making bread at home since a good hot oven at beginning of cooking is important to a good rise, and also for sensitive bakery items like pastry, cookies, etc..
I'm a bit passionate about this subject because I used to have a crappy oven in university and would put in a sheet pan of pastry to cookies and the oven would cycle on and heat way beyond what it was set to, scortching the bottoms of the product. Pre-heating to 40-50F higher than the required setting worked a charm since I could get the goods into the oven and close the door, then turn the oven down to 350 and the element wouldn't cycle on and blacken the bottom of the pastries.
