Option 1 states that a microwave oven uses waves with a large wavelength in the invisible range. This means that the waves used by a microwave oven have a long distance between each wave and cannot be seen by the human eye. This option correctly describes the type of waves used by a microwave oven.

Option 2 states that a microwave oven uses waves with a small wavelength in the visible range. This option is incorrect because waves with a small wavelength in the visible range are typically referred to as visible light, which is not used by a microwave oven.

Option 3 states that a microwave oven uses waves with a large wavelength in the visible range. This option is incorrect because waves with a large wavelength in the visible range would be in the form of infrared radiation, not microwaves.

Option 4 states that a microwave oven uses waves with a small wavelength in the invisible range. This option is incorrect because microwaves have a larger wavelength and can be classified as radio waves, which are invisible to the human eye.

In summary, option 1 is the correct answer as it correctly describes microwaves as having a large wavelength in the invisible range.